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-branches/SKILL.md

@@ -0,0 +1,66 @@
+---
+name: gitea-branches
+
+description: >
+  Use when managing Gitea repository branches — listing, creating, or deleting
+  branches — or inspecting commit history within a Gitea repo: listing commits
+  (optionally filtered by branch or file path) or getting full detail for a
+  single commit by SHA. Triggers on "list branches", "create a branch",
+  "delete a branch", "what commits are on this branch", "show commit <sha>",
+  "what changed in that commit" — even if the user doesn't say "Gitea"
+  explicitly, as long as the repo's remote is a Gitea instance. Do not use for
+  local git branch/commit operations on your working copy (use git-branches or
+  git-history) or for PR-side branch references like cross-repo fork PR heads
+  (use gitea-prs).
+
+compatibility: Requires Gitea MCP server configured with a token with write:repository scope; this is confirmed to gate list_branches, create_branch, and delete_branch (Gitea gates reads behind write scope for repo-scoped operations), and is inferred by analogy (not explicitly confirmed by source docs) to also gate list_commits and get_commit. Requires git remote "origin" pointing to the Gitea instance.
+
+metadata:
+  category: integration
+  version: "0.1.1"
+  source_keys:
+    - gitea-mcp-repo
+    - gitea-mcp-slim-go
+    - context7-websites-gitea
+
+allowed-tools: Bash mcp__gitea__list_branches mcp__gitea__create_branch mcp__gitea__delete_branch mcp__gitea__list_commits mcp__gitea__get_commit
+---
+
+## Gotchas
+
+- **Never delete a protected branch (`main`/`master` by name, or `protected: true` from `list_branches`) without explicit confirmation.** `delete_branch` is a direct API call, not a local `git push` — there is no client-side force-push guard protecting it. Name-matching `main`/`master` is a convenient default but not authoritative — a repo can protect a differently-named default branch. When in doubt, call `list_branches` first and check `protected` on the target; treat deletion of any protected branch as a hard refusal unless the user explicitly confirms in the conversation.
+- **404 may actually mean 403.** Gitea hides permission errors as not-found to avoid leaking resource existence. If any of these five tools returns 404 unexpectedly, check token scope (see `references/branches.md` / `references/commits.md`) before concluding the branch or commit doesn't exist.
+- **Pagination is manual.** `list_branches` and `list_commits` return one page at a time — no auto-pagination in the MCP layer. When you need a complete list, iterate `page: 1, 2, ...` until the returned count is less than `per_page`.
+- **Owner/repo always come from the git remote, never from `get_me`.** Resolve them via `git remote get-url origin` (Step 1 below). `get_me`/`list_my_repos` are blocked under the token scopes this skill assumes.
+- **`create_branch`'s source is `old_branch`, not "wherever gitea-mcp feels like."** Omitting `old_branch` forks from the repo's server-side default branch — not necessarily the branch you're currently working on locally. If you want to branch from your current checkout, pass `old_branch` explicitly.
+
+## Step 1 — Resolve owner and repo
+
+Before any tool call, extract `owner` and `repo` from the git remote:
+
+```bash
+git remote get-url origin
+```
+
+If origin is not set or the URL is not a Gitea URL, stop and report: "No Gitea remote found — set origin to your Gitea instance URL."
+
+## Step 2 — Dispatch
+
+| Invocation | Action |
+|---|---|
+| `/gitea-branches` or `/gitea-branches list` | List branches |
+| `/gitea-branches create <name> [from <base>]` | Create branch |
+| `/gitea-branches delete <name>` | Delete branch |
+| `/gitea-branches commits [on <branch>] [touching <path>]` | List commit history |
+| `/gitea-branches commit <sha>` | Get full detail for one commit |
+
+For branch operations (list/create/delete), read `references/branches.md`.
+For commit operations (list/get), read `references/commits.md`.
+
+## Step 3 — Report
+
+For reads: display branches as name + protected flag; display commits as SHA (short), message summary, author, date.
+
+For writes (create/delete): confirm the action taken, the branch name, and (for create) the base it forked from.
+
+For errors: surface the HTTP code and message. If a 404 is unexpected, re-check token scope per the Gotchas above before reporting "not found" to the user.