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/gitea/skills/gitea-files/SKILL.md

@@ -0,0 +1,56 @@
+---
+name: gitea-files
+
+description: >
+  Use when reading or writing individual files or directory trees in a Gitea repository via the
+  Gitea MCP server: reading a file's contents, listing a directory, walking a full repository
+  tree, creating a new file, updating an existing file, or deleting a file. Triggers on "read this
+  file from the repo", "what's in this directory", "show me the repo tree", "create/update a file
+  in Gitea", "commit this file to the branch", "delete this file from the repo" — even when the
+  user doesn't say "Gitea" explicitly, as long as the target is a Gitea-hosted repository. Do not
+  use for local filesystem file operations (use Read/Write/Edit), for branch or commit history
+  (use gitea-branches), or for opening a pull request around a file change (use gitea-prs after
+  the file write completes here).
+
+compatibility: Requires the Gitea MCP server configured with a token scoped to at least
+  write:repository. Tested with a token holding write:issue + write:repository; write:issue
+  is not actually required for any of this domain's five tools.
+
+metadata:
+  category: gitea
+  source_keys:
+    - gitea-mcp-repo
+    - gitea-mcp-slim-go
+    - context7-websites-gitea
+
+allowed-tools: mcp__gitea__get_file_contents mcp__gitea__get_dir_contents mcp__gitea__get_repository_tree mcp__gitea__create_or_update_file mcp__gitea__delete_file
+---
+
+## Gotchas
+
+- **A 404 from any read call may actually be a 403 in disguise.** `get_file_contents`, `get_dir_contents`, and `get_repository_tree` all gate on `write:repository` scope, not just read access — some Gitea endpoints return 404 instead of 403 when the token's scope is insufficient, to avoid leaking whether the resource exists. If a read fails with 404 on a path you're confident is correct, check the token's configured scopes before concluding the file or directory doesn't exist.
+- **SHA is the concurrency token for every write — and it lives at the top level of `get_file_contents`'s response, not nested under `content`.** `create_or_update_file` without `sha` is always treated as a *create*: if the path already exists, Gitea returns HTTP 409. `delete_file` has no optional path at all — omitting `sha` returns HTTP 422. The safe sequence for any update or delete is always: call `get_file_contents` first, read the top-level `sha` field, then pass that exact value to the write call. Never guess or reuse a stale SHA — a mismatched SHA is rejected the same as a missing one.
+- **A write can also fail because the branch requires signed commits — a separate failure mode from a bad SHA.** `create_or_update_file` and `delete_file` create commits server-side via a bare API token call with no 2FA/PGP context. If the target branch's protection rule requires signed commits, Gitea rejects the write outright — surfaced as a generic 403 or 422, not an error naming "signed commit required," and reads against that same branch keep succeeding right up until you try to write. When a write fails without a clean 409 (missing/stale SHA) or 404 (bad path) explanation, check whether the branch's protection rule requires signed commits before assuming the SHA is wrong and retrying.
+- **A large `create_or_update_file` payload can hit a reverse-proxy 413 that has nothing to do with Gitea.** `content` is base64-encoded, which inflates the payload ~33% over the raw file size; a 413 is commonly a reverse-proxy body-size limit in front of the Gitea instance, not a Gitea-side rejection. No amount of retrying, or changing the SHA, path, or branch, will fix it — it needs the proxy's config raised, which is outside this skill's or the calling agent's control. Surface that distinction to the user instead of retrying the same call.
+- **`get_dir_contents` and `get_repository_tree` are not SHA sources for a specific file's write.** `get_dir_contents` entries carry no `sha` at all. `get_repository_tree` entries do carry a `sha` (a blob/tree hash), but fetching it means an extra round trip with no content — `get_file_contents` is the canonical path since it returns the decoded content and the write-ready `sha` in one call.
+- **`owner` and `repo` are always caller-supplied inputs, never resolved here.** This skill doesn't infer them from a git remote. If invoked directly by a human, ask for them if not stated. If invoked by `gitea-workflow` or an orchestrating agent, expect them to already be resolved and passed in.
+- **Direct commits to a branch are a first-class action, not a workaround.** Gitea's own web UI defaults to editing files directly against a branch — `create_or_update_file`/`delete_file` used that way is normal, not an API escape hatch to avoid. The SHA-currency requirement above is the actual risk to manage, not the act of committing directly.
+- **`ref` (reads) vs. `branch_name` (writes) are different parameters for the same concept.** `get_file_contents`, `get_dir_contents`, and `get_repository_tree` (as `tree_sha`) all accept a branch name, tag, or commit SHA to select what to read. `create_or_update_file` and `delete_file` instead take `branch_name` — the branch the commit lands on. Don't conflate the two when chaining a read into a write.
+- **Content is base64.** `create_or_update_file`'s `content` parameter is base64-encoded file content, not raw text — encode before calling. `get_file_contents`'s response content is likewise base64-encoded (decode after reading), unless `withLines: true` is passed for a numbered-line view.
+
+## Reading
+
+- **Single file:** `get_file_contents(owner, repo, ref, path)`. Pass `withLines: true` only when you need line numbers for referencing specific lines (e.g. quoting a snippet back to the user); omit it for a normal content fetch.
+- **One directory level:** `get_dir_contents(owner, repo, ref, path)` — returns immediate entries only (name, path, type, size), no recursion, no SHA, no content.
+- **Whole tree:** `get_repository_tree(owner, repo, tree_sha, recursive)` — `tree_sha` accepts a SHA, branch, or tag name despite the name. Set `recursive: true` to walk subdirectories in one call. Response includes `truncated: true` when a page doesn't hold every entry — page through with `page`/`per_page` (default `page: 1`, `per_page: 30`) until you get fewer results than `per_page`.
+
+## Writing
+
+- **Creating a new file:** call `create_or_update_file(owner, repo, path, content, message, branch_name)` with `sha` omitted entirely.
+- **Updating an existing file:** call `get_file_contents(owner, repo, ref: branch_name, path)` first, take the top-level `sha`, then call `create_or_update_file(..., sha: <that value>)`.
+- **Deleting a file:** call `get_file_contents` first the same way, then `delete_file(owner, repo, path, message, branch_name, sha: <that value>)` — `sha` is required, no create-style fallback exists.
+- **Creating a new branch as part of the write:** pass `new_branch_name` on `create_or_update_file` to branch off before the commit lands, instead of calling a separate branch-creation step.
+
+If the change needs review before merging, or targets a protected branch, hand off to `gitea-prs` after the write lands here to open the pull request — this skill's scope ends at the commit.
+
+If you need the full multi-call sequence rather than the single-call summary above — e.g. branching off as part of a file push ahead of opening a PR, or recovering a SHA you didn't capture earlier — read `references/examples.md`.