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/git-history/SKILL.md

@@ -0,0 +1,96 @@
+---
+name: git-history
+
+description: >
+  Inspect git history: query logs with pickaxe, line-range, or custom formats; find bug origins via bisect; locate problematic commits for cherry-picking or reverting. Use when investigating history, tracing when a change happened, or finding the commit that broke something. Return structured results for downstream agents. Do not use for authoring or formatting commit messages, or executing rebase/squash/fixup operations — use git-commits for that.
+
+metadata:
+  category: git
+  source_keys:
+    - git-scm-bisect-docs
+    - git-scm-log-docs
+    - git-scm-diff-docs
+
+allowed-tools: Bash
+---
+
+## Gotchas
+
+- **Pickaxe searches (`-S` vs `-G`)**: `-S"string"` finds commits where string count changed; `-G"regex"` finds any line matching regex in diffs. They're not equivalent: a line replaced (one removal + one addition) matches `-G` but not `-S` if count is unchanged.
+- **`--follow` only works for single files**: it traces renames but fails with multiple paths or directory globs. Use `git log -- <single-file>` or query without `--follow`.
+- **Bisect with skips**: if bisect cannot pinpoint a commit because the culprit is adjacent to skipped commits, it reports "cannot find exact culprit" and lists candidates. This is not a failure — it's as precise as the skip range allows.
+- **Interactive rebase is non-recoverable on mistake**: there's no undo once `rebase -i` starts. Suggest `git reflog` to recover if the user realizes mid-way they selected the wrong commits.
+- **`-L` (line-range history) requires exact line numbers or regex patterns**: off-by-one errors omit the target range. Test the range with `git log -L` before offering it to users.
+
+## Query Logs and Locate Commits
+
+Default to `git log --oneline` for quick inspection. For deeper queries:
+
+- **Find when a string appeared or disappeared**: Use `git log -S"string"` (count-sensitive, finds adds/removes). If you need any mention of the string in diffs, use `git log -G"regex"` instead. Add `--pickaxe-regex` to treat the `-S` string as a POSIX ERE, and `--pickaxe-all` to show every changed file in a matching changeset, not just the matching ones. Binary files are searched by `-S`; `-G` ignores them unless `--text` is also supplied.
+- **Trace changes to a specific line or function**: Use `git log -L <start>,<end>:<file>` or `git log -L :<function>:<file>` (requires function name heuristic). This shows the evolution of that range across all commits.
+- **Filter by change type**: Use `git log --diff-filter=<type>` (A=added, M=modified, D=deleted, R=renamed) to narrow to specific file operations.
+- **Mainline-only history through merges**: Use `--first-parent` to follow only the integration branch and skip merged-in side-branch commits; combine with `--merges`/`--no-merges` or `--ancestry-path`/`--min-parents`/`--max-parents` for other ancestry-graph filtering — see `references/git-log-format.md` for the full set.
+- **Custom format for structured output**: Construct format string with `%h` (hash), `%s` (subject), `%an` (author), `%ar` (relative date), `%b` (body). Example: `git log --format="%h | %s | %an (%ar)"`.
+- **File-specific history with renames**: Use `git log --follow -- <file>` (single file only). Without `--follow`, log stops at the rename boundary.
+
+## Bisect to Find Blame Commit
+
+Use bisect when hunting for the commit that introduced a bug or behaviour change. Binary search reduces iterations from O(N) to O(log N).
+
+**Basic manual flow:**
+```bash
+git bisect start
+git bisect bad [HEAD]        # mark current (or specified) as broken
+git bisect good <commit>     # mark known-good baseline
+# Git checks out midpoint; test it manually
+git bisect good              # if test passes
+git bisect bad               # if test fails
+# Repeat until git reports "X is the first bad commit"
+git bisect reset             # return to original HEAD
+```
+
+**Automated with `git bisect run`:** if a test command exists, use `git bisect run <cmd>`. Git interprets the exit code: `0`=good, `1-124`=bad, `125`=skip (build broken), `126-127`=POSIX shell errors treated as bad, `128+`=**aborts the bisect session entirely** (not treated as bad — a crashed test script can silently end the search).
+
+**With skip:** if a commit is untestable (broken build), use `git bisect skip` to exclude it without manually deciding good/bad. If the first-bad is adjacent to skips, bisect reports it cannot pinpoint but lists candidates.
+
+**Undoing a wrong good/bad call:** `git bisect log` prints the session's decision history; save it (`git bisect log > bisect.log`), edit out the mistaken entry, then `git bisect reset && git bisect replay bisect.log` to resume from the corrected log instead of restarting the whole search.
+
+**Narrowing and speeding up the search:** `git bisect start HEAD v1.2 -- src/` limits bisection to a path, cutting the number of trials. `--no-checkout` updates the `BISECT_HEAD` ref instead of checking out a working tree (useful for tests that don't need one; automatic in bare repos). `--first-parent` follows only first parents at merges, finding the integration commit that introduced a regression while ignoring broken side branches.
+
+**Inspecting remaining candidates visually:** `git bisect visualize` (alias `view`) opens the suspects in gitk; add `--stat` or `-p` to show diffstat or full patches instead. Falls back to `git log` when no graphical display is detected.
+
+**For non-regression hunts:** use `git bisect start --term-new <new> --term-old <old>` to search for a property change instead of a bug (e.g., performance regression). Then use the custom terms instead of `good`/`bad`.
+
+For rebase execution (interactive rebase, squash/fixup/reword, conflict handling) see git-commits — it owns history-rewriting operations. This skill only locates commits and reports on history; it does not execute rebases.
+
+## Find and Manipulate Problematic Commits
+
+Once a commit is identified (via log query or bisect), offer cherry-pick or revert. This section is general git knowledge, not sourced from `history-inspection.md` — `git-branches`'s SKILL.md explicitly delegates cherry-pick/revert here (see its Merging section), which is why this skill carries them rather than treating them as out of scope:
+
+- **Cherry-pick**: `git cherry-pick <commit>` copies a commit's changes onto current HEAD. Use when backporting fixes to other branches.
+- **Revert**: `git revert <commit>` creates a new commit that undoes the changes. Use when un-applying a merged commit without rewriting history.
+- **Blame for context**: `git blame <file>` shows which commit last changed each line. Use to trace a specific line back to its introducing commit.
+
+## Inspect Diffs
+
+Diff-output tuning is in scope too: `--stat` for a diffstat summary, `--word-diff` for word-level (not line-level) changes, and whitespace flags (`-w`, `--ignore-blank-lines`) to suppress noise from reformatting. See `references/git-log-format.md` for the full flag set.
+
+## Return Results Structured
+
+For agent consumption, return:
+- **Commit SHA** (full or abbreviated as appropriate)
+- **Subject line** (from `%s`)
+- **Author and date** (from `%an` and `%ar`)
+- **Action taken or recommended** (e.g., "Found via bisect", "Offer cherry-pick to main", "Rebase conflicts detected")
+
+Example for agent:
+```
+Found first bad commit: abc1234
+Subject: fix null pointer in parser
+Author: Alice (2 weeks ago)
+Recommendation: Backport to release branch via cherry-pick
+```
+
+## Reference
+
+For the full log format placeholder catalogue, named format presets, `--diff-filter` letters, `-L` range syntax, ancestry filters, and `git diff` output-control flags, read `references/git-log-format.md`.