refactor(gitea-branches): retrofit to the ADR-0020 context contract

Description 688 -> 282 chars, body 435 -> 293 words, Gotchas 5 entries/54% of
body -> 3/23.5%. Clears the description FAIL and the Gotchas suggestion.

Cut the second trigger register (six re-quoted user phrasings) and the capability
enumeration; both moved to a new Boundaries section in the skill's own README.
Kept all three boundary clauses -- git-branches, git-history and gitea-prs each
defend a real activation steal, and gitea-prs is now the only guard on the
branch/PR collision in either direction since gitea-prs's own retrofit narrowed
its boundary to issues. Written as one arrow per target: the resolver extracts
only the first name per arrow clause, so conjoined targets go unchecked.

Two Gotchas deleted -- one paraphrased the step below it (its non-obvious half,
the get_me/list_my_repos token-scope block, was folded into that step), the other
is carried in full by references/branches.md:40-52.

Repoint two reference pointers the rename broke: branches.md and commits.md named
Gotchas by titles this retrofit changed. Now named by stable descriptors.

Refs #99

plugins/gitea/.apm/skills/gitea-branches/SKILL.md

@@ -2,22 +2,16 @@
 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).
+  Use when listing, creating, or deleting branches in a Gitea repository, or
+  reading its commit history — even when the user does not say "Gitea". Not a
+  local working copy's branches -> `git-branches`. Not local history ->
+  `git-history`. Not a PR's head or base branch -> `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"
+  version: "0.1.2"
   source_keys:
     - gitea-mcp-repo
     - gitea-mcp-slim-go
@@ -28,11 +22,9 @@ allowed-tools: Bash mcp__gitea__list_branches mcp__gitea__create_branch mcp__git
 
 ## 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.
+- **404 often means 403.** Gitea masks permission errors as not-found; on an unexpected one, check token scope before reporting a branch or commit missing.
+- **Nothing auto-paginates.** `list_branches` and `list_commits` return one page; iterate `page` until the returned count is below `per_page`.
+- **`delete_branch` has no force-push guard.** Check `protected` from `list_branches` first and require explicit confirmation — a protected branch need not be named `main`.
 
 ## Step 1 — Resolve owner and repo
 
@@ -42,7 +34,7 @@ Before any tool call, extract `owner` and `repo` from the git remote:
 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."
+`get_me` and `list_my_repos` are blocked under the token scope this skill assumes, so the remote is the only source. 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
 
@@ -54,7 +46,7 @@ If origin is not set or the URL is not a Gitea URL, stop and report: "No Gitea r
 | `/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 branch operations (list/create/delete), read `references/branches.md` — it carries the call signatures, the `old_branch` source rule, and the protected-branch refusal in full.
 For commit operations (list/get), read `references/commits.md`.
 
 ## Step 3 — Report
@@ -63,4 +55,4 @@ For reads: display branches as name + protected flag; display commits as SHA (sh
 
 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.
+For errors: surface the HTTP code and message, applying the 404 gotcha above before reporting "not found" to the user.