fix(kyberforge): bridge apm content to Claude Code's flat plugin discovery

Claude Code's (and Copilot's) native plugin installer has zero awareness of
.apm/ nesting -- it convention-scans only flat skills/, agents/, commands/,
hooks.json at each plugin's root. Confirmed via strings on the installed
claude binary and live installs of git@holocron/gitea@holocron/kyberforge@
holocron, all reporting Skills(0) Agents(0) Hooks(0) post ADR-0015's apm
conversion. Root cause (apm_cli/core/plugin_manifest.py): apm's plugin.json
compiler deliberately strips skills/agents/commands keys, assuming the host
already auto-discovers those convention directories -- it has no model of
.apm/ being host-visible at all. Separately, apm's own bundle exporter
(apm_cli/bundle/plugin_exporter.py, behind `apm pack --format plugin`)
implements the correct .apm/ -> flat mapping, but only ever targeted
build/<name>-<version>/, a path nothing in marketplace.json's source: points
at.

scripts/sync-plugin-content.sh wraps that bundle exporter and copies its
agents/, skills/, commands/, instructions/, extensions/, and merged
hooks.json back into each plugin's own root as a second tracked
compiled-output category -- same governance status as
.claude-plugin/plugin.json: generated from .apm/, never hand-edited. tests/
subdirectories are excluded from the mirror (dev fixtures, not host-visible
runtime content; several hardcode a relative repo-root walk-up sized for the
.apm/-nested depth, which breaks when duplicated one level shallower).
Applied for real across all 6 plugins and verified two ways: `claude plugin
validate --strict` passes on every real plugin directory, and a live
`claude --plugin-dir <path> -p "list skills/agents"` behavioral test
confirms content is now actually discovered.

Also, from the same issue #90 review round:
- scripts/check-manifests.sh pointed at each plugin's root-level plugin.json
  (checking skills/hooks/mcpServers/agents pointer fields) -- that file was a
  stale near-duplicate of .claude-plugin/plugin.json nothing else read or
  wrote, now deleted across all 6 plugins. check-manifests.sh is rewritten to
  validate .claude-plugin/plugin.json instead, and drops the pointer-field
  checks entirely (nothing to check -- those fields are correctly absent by
  design). Content-presence drift is now check-plugin-content-sync's job, a
  new pre-push hook wired in .pre-commit-config.yaml.

docs/adr/0017 records the root cause and decision in full, including two
rejected alternatives (patching plugin.json's path fields directly -- apm's
compiler strips them on every run; pointing marketplace.json at apm pack's
build/ output -- a version-suffixed non-source directory nothing can install
from without an extra build step). ADR-0015 and CONTEXT.md are updated to
point at it.

Refs: #90

plugins/git/skills/pc-author/README.md

@@ -0,0 +1,24 @@
+# pc-author
+
+Create, add, remove, update, and configure `.pre-commit-config.yaml`.
+
+## What it does
+
+Manages the pre-commit configuration file in any git repo. When invoked, it scans the repo for languages, proposes appropriate hooks with rationale, and writes or modifies `.pre-commit-config.yaml`. It validates every write with `pre-commit validate-config` and flags stale revision pins. It does not run hooks or install them into `.git/hooks/` — use `pc-run` for that.
+
+## Usage
+
+```
+/pc-author
+```
+
+Invoke with no arguments. The skill determines from context whether to create a new config or modify an existing one.
+
+## Files
+
+| File | Purpose |
+|------|---------|
+| `SKILL.md` | Skill instructions for agents |
+| `references/hooks-by-language.md` | Hook recommendations by detected language/extension |
+| `references/README.md` | Index of files in references/ |
+| `references/sources.md` | Provenance — research sources that informed this skill |

plugins/git/skills/pc-author/SKILL.md

@@ -0,0 +1,91 @@
+---
+name: pc-author
+description: >
+  Use when the user wants to create, add hooks to, remove hooks from, update,
+  or configure .pre-commit-config.yaml. Triggers on: "set up pre-commit",
+  "add a hook", "remove this hook", "configure pre-commit", "create a pre-commit
+  config", "disable trailing whitespace hook", "add shellcheck", "update my
+  pre-commit config", even if the user does not name pre-commit explicitly.
+  Do not use for running hooks, installing git hooks, or bumping revision pins
+  — use pc-run for those.
+allowed-tools: Bash Read Write Edit
+metadata:
+  category: devtools
+  source_keys:
+    - context7-pre-commit-com
+    - pre-commit-com
+    - context7-pre-commit-hooks
+    - pre-commit-hooks-github
+---
+
+## Gotchas
+
+- `rev` must be an immutable tag or commit SHA — never a branch name. `pre-commit autoupdate` breaks silently on branches.
+- Fixers (`trailing-whitespace`, `end-of-file-fixer`, `pretty-format-json`) modify files but do NOT auto-stage them. The commit is blocked; the user must re-stage and recommit. Warn when adding fixers.
+- `pre-commit validate-config` catches YAML structure errors but does NOT check whether hook `id`s exist in the target repo's manifest, and does NOT download or run hooks. It is fast; run it after every write.
+- When removing a hook leaves its repo block with zero hooks, delete the entire repo block — an empty `hooks: []` causes `validate-config` to fail.
+- `language: system` and `language: script` are deprecated names. Use `language: unsupported` and `language: unsupported_script` for new local hooks.
+
+## Route
+
+Check before acting:
+
+- `.pre-commit-config.yaml` does not exist → **Create from scratch**
+- File exists → **Modify existing**
+
+## Create from scratch
+
+1. Run a shallow extension scan:
+   ```bash
+   git ls-files | grep -oE '\.[a-z]+$' | sort | uniq -c | sort -rn
+   ```
+2. Read `references/hooks-by-language.md` to map detected extensions to recommended hooks. For a minimal starting point instead of a full recommendation set, `pre-commit sample-config > .pre-commit-config.yaml` prints a small starter config to build on.
+3. State the proposed config in full before writing. Wait for user confirmation.
+4. Write `.pre-commit-config.yaml`.
+5. Run `pre-commit validate-config`. If non-zero: show the error, fix it, re-validate. Never leave a broken config.
+
+## Modify existing
+
+Read `.pre-commit-config.yaml` first. Note any stale `rev` values (see **Rev staleness** below) but do not change them.
+
+### Adding a hook
+
+1. Run a shallow extension scan to detect languages in the repo:
+   ```bash
+   git ls-files | grep -oE '\.[a-z]+$' | sort | uniq -c | sort -rn
+   ```
+2. Read `references/hooks-by-language.md` for the correct repo URL, rev, and recommended args for any hook before writing.
+3. Check for duplicates — if the same hook ID or equivalent tool already exists in the config, say so and stop.
+4. To sanity-check a hook against the repo's actual files before committing to it in config, smoke-test it with `pre-commit try-repo <repo-url> <hook-id> --verbose` (or a local path for hooks under development). This runs the hook without writing anything.
+5. If the hook's source repo already exists in the config, add the hook under that repo block. Otherwise append a new repo block.
+6. State the proposed addition. Wait for confirmation.
+7. Write. Run `pre-commit validate-config`. If non-zero: show error, fix, re-validate.
+
+### Removing a hook
+
+1. Identify the hook entry and its repo block.
+2. State what will be removed: hook ID, and whether the parent repo block will also be deleted (if it would have zero hooks remaining). Wait for confirmation.
+3. Remove the hook entry. If the repo block now has zero hooks remaining, remove the entire repo block.
+4. Write. Run `pre-commit validate-config`. If non-zero: revert the edit, show the error, and stop — do not leave a broken config (removal edits are not safely auto-fixable, unlike a bad new hook block, which can usually be corrected in place).
+
+### Configuring top-level keys
+
+Only when the user explicitly asks. Valid keys: `fail_fast`, `default_stages`, `default_language_version`, `minimum_pre_commit_version`, `exclude`, `files`, `default_install_hook_types`.
+
+State the proposed change and wait for confirmation before writing.
+
+## Rev staleness
+
+When reading the config, for each repo listed in `references/hooks-by-language.md`, compare its `rev` in the user's config against the rev in that file. Flag any mismatch as potentially outdated and tell the user to run `pc-run` to autoupdate. Repos not in the reference cannot be checked — skip them silently. Do not modify `rev` values yourself.
+
+The reference table's pins can themselves go stale between updates — treat a mismatch as a prompt to check, not a certainty. `pre-commit autoupdate` (via `pc-run`) is the authoritative source for what the current rev actually is.
+
+## Scope boundary
+
+This skill manages `.pre-commit-config.yaml` only. It does not:
+- Author `.pre-commit-hooks.yaml` (publishing hooks for external consumers)
+- Run `pre-commit install`
+- Execute hooks or run the test suite
+- Bump `rev` values
+
+For those operations, use `pc-run`.

plugins/git/skills/pc-author/references/README.md

@@ -0,0 +1,14 @@
+---
+source_keys:
+  - context7-pre-commit-com
+  - pre-commit-com
+  - context7-pre-commit-hooks
+  - pre-commit-hooks-github
+---
+
+# references/
+
+| File | Purpose |
+|---|---|
+| `hooks-by-language.md` | Hook recommendations by language/context — repo, rev, and rationale for adding hooks |
+| `sources.md` | Provenance: research sources that informed this skill |

plugins/git/skills/pc-author/references/hooks-by-language.md

@@ -0,0 +1,120 @@
+---
+source_keys:
+  - context7-pre-commit-com
+  - pre-commit-com
+  - context7-pre-commit-hooks
+  - pre-commit-hooks-github
+---
+
+# Hook Recommendations by Language / Context
+
+Use this table when creating a config from scratch or recommending hooks to add.
+Always check the existing config for duplicates before proposing.
+
+## Universal (recommend for every repo)
+
+| Hook ID | Repo | Rev | Rationale |
+|---------|------|-----|-----------|
+| `end-of-file-fixer` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Ensures files end with a newline — prevents spurious diffs |
+| `trailing-whitespace` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Strips trailing whitespace — prevents invisible diff noise |
+| `check-merge-conflict` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Catches unresolved merge markers before commit |
+| `detect-private-key` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Blocks PEM private key material |
+| `check-added-large-files` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Blocks accidentally committing large binary files |
+| `check-case-conflict` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Catches filenames that would collide on case-insensitive filesystems |
+| `mixed-line-ending` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Normalizes line endings |
+| `no-commit-to-branch` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Blocks direct commits to protected branches — defaults to blocking `main`+`master` with no args; add `args: [--branch, <name>]` only to protect additional branch names |
+
+## Shell (`.sh`)
+
+| Hook ID | Repo | Rev | Rationale |
+|---------|------|-----|-----------|
+| `shellcheck` | `https://github.com/jumanjihouse/pre-commit-hooks` | `3.0.0` | **Unverified — not in research corpus, verify upstream before use.** Static analysis for shell scripts; catches common errors |
+
+Recommended args: `args: [--severity=warning]`
+
+## Python (`.py`)
+
+| Hook ID | Repo | Rev | Rationale |
+|---------|------|-----|-----------|
+| `check-ast` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Validates Python files parse as valid AST |
+| `check-builtin-literals` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Enforces literal syntax for `dict()`, `list()` |
+
+For formatting: check if `black`, `ruff`, or `isort` is already configured in `pyproject.toml` before recommending them.
+
+## JSON (`.json`)
+
+| Hook ID | Repo | Rev | Rationale |
+|---------|------|-----|-----------|
+| `check-json` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Validates JSON parses correctly |
+| `pretty-format-json` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Auto-formats JSON (fixer — warns user to re-stage after commit) |
+
+## YAML (`.yaml`, `.yml`)
+
+| Hook ID | Repo | Rev | Rationale |
+|---------|------|-----|-----------|
+| `check-yaml` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Validates YAML parses correctly |
+
+For Kubernetes/Helm YAML with custom tags, add `args: ['--unsafe']` and `exclude: ^helm/templates/`.
+
+## TOML (`.toml`)
+
+| Hook ID | Repo | Rev | Rationale |
+|---------|------|-----|-----------|
+| `check-toml` | `https://github.com/pre-commit/pre-commit-hooks` | `v6.0.0` | Validates TOML parses correctly |
+
+## Secrets / security
+
+| Hook ID | Repo | Rev | Rationale |
+|---------|------|-----|-----------|
+| `gitleaks` | `https://github.com/gitleaks/gitleaks` | `v8.30.1` | **Unverified — not in research corpus, verify upstream before use.** Scans for secrets and high-entropy strings |
+
+## Commit message
+
+| Hook ID | Repo | Rev | Stage | Rationale |
+|---------|------|-----|-------|-----------|
+| `conventional-pre-commit` | `https://github.com/compilerla/conventional-pre-commit` | `v2.4.0` | `commit-msg` | Enforces Conventional Commits format |
+
+When adding commit-msg hooks, also add `default_install_hook_types: [pre-commit, commit-msg]` to the top-level config if not already present.
+
+## Meta-validation (add last, after all other repos)
+
+```yaml
+- repo: meta
+  hooks:
+    - id: check-hooks-apply       # catches hooks that match no files
+    - id: check-useless-excludes  # catches exclude patterns that match no files
+```
+
+## Local hooks (repo: local)
+
+Use for repo-specific scripts that don't belong in an external hook repo.
+
+```yaml
+- repo: local
+  hooks:
+    - id: run-tests
+      name: Run test suite
+      entry: bash tests/run-tests.sh
+      language: unsupported_script
+      pass_filenames: false
+      always_run: true
+      stages: [pre-push]
+```
+
+Language choices for local hooks:
+- `unsupported` — system PATH tool (pre-commit does not manage env)
+- `unsupported_script` — script at a repo-relative path
+- `fail` — always-fail guard; `entry` text becomes the error message
+- `python` — isolated venv; use `additional_dependencies` for pip packages
+- `node` — isolated node env; `additional_dependencies` are npm packages
+- `ruby` — isolated gem env; `additional_dependencies` are gems
+- `golang` — builds from source; `additional_dependencies` are Go module paths
+- `rust` — Cargo build
+- `docker` — Docker image built from `entry`; use when no other language fits
+- `docker_image` — pulls a pre-built Docker image by `entry`
+- `conda` — Conda environment; conda-native hooks
+- `coursier` — Coursier (Scala/JVM) environment; JVM hooks
+
+## Rev pin freshness
+
+The revs above were last verified current at time of writing (matched against the plugin's own research corpus in `docs/research/docs/pre-commit/`; rows marked "Unverified" have no such backing and must be checked against upstream before use). Since `pc-author`'s "Rev staleness" check treats this table as ground truth, a pin that goes stale here produces false-positive staleness warnings for users who already have a newer, correct rev. Re-verify these pins periodically (e.g. against each repo's latest release tag). When in doubt, treat `pre-commit autoupdate`'s own output as the authoritative staleness signal, not a mismatch against this table.

plugins/git/skills/pc-author/references/sources.md

@@ -0,0 +1,33 @@
+# Sources
+
+## context7-pre-commit-com
+
+- **URL:** context7:/pre-commit/pre-commit.com
+- **Description:** Official pre-commit.com documentation — installation, configuration schema, CLI reference, hook authoring, advanced features, troubleshooting
+- **Contributing files:** SKILL.md, references/hooks-by-language.md
+- **Research doc:** plugins/git/docs/research/docs/pre-commit/{overview,configuration,cli-reference,hook-authoring}.md
+- **Status:** `extracted`
+
+## pre-commit-com
+
+- **URL:** https://pre-commit.com/
+- **Description:** Pre-commit framework homepage — full docs covering install, config, CLI, hook authoring, stages, local hooks, meta hooks, hazmat helpers, CI integration
+- **Contributing files:** SKILL.md, references/hooks-by-language.md
+- **Research doc:** plugins/git/docs/research/docs/pre-commit/{overview,configuration,cli-reference,hook-authoring}.md
+- **Status:** `extracted`
+
+## context7-pre-commit-hooks
+
+- **URL:** context7:/pre-commit/pre-commit-hooks
+- **Description:** Official pre-commit-hooks collection — all available hook IDs with options and examples
+- **Contributing files:** references/hooks-by-language.md
+- **Research doc:** plugins/git/docs/research/docs/pre-commit/hooks-reference.md § pre-commit-hooks (official collection)
+- **Status:** `extracted`
+
+## pre-commit-hooks-github
+
+- **URL:** https://raw.githubusercontent.com/pre-commit/pre-commit-hooks/main/README.md
+- **Description:** Official pre-commit-hooks README — complete hook listing with all args, categories, deprecated hooks, and latest version (v6.0.0)
+- **Contributing files:** references/hooks-by-language.md
+- **Research doc:** plugins/git/docs/research/docs/pre-commit/hooks-reference.md § pre-commit-hooks (official collection), § Deprecated hooks
+- **Status:** `extracted`