[AI] Add Claude Code skills for docs, commits, and PR review (#7967)

* [AI] Add Claude Code skills for docs, commits, and PR review

Add three project-scoped skills under .claude/skills/ so any contributor
using Claude Code in this repo gets the same conventions applied
automatically: writing-actual-docs (points Claude at writing-docs.md
before any docs work), committing-actual-changes (points Claude at
pr-and-commit-rules.md before any commit/PR so the [AI] prefix and
template-blank rule are followed), and review-actual-pr (end-to-end
offline PR review with browser testing via playwright-cli, never posts
to GitHub).

All skill paths and tool assumptions are repo-relative (resolved via
git rev-parse --show-toplevel) so they work on any contributor's
machine, not just the author's.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* [AI] Fix remaining hardcoded $HOME path in PR-review playbook

The Step 3 highlight-overlay example still referenced
$HOME/.claude/skills/review-actual-pr/... which only resolves on
the original author's machine. Switch to the same git rev-parse
--show-toplevel pattern used elsewhere in the skill so it works
for any contributor with a checkout of the repo.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* [AI] Add release note for #7967

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* [AI] Drop "add AI generated label" instruction now that it auto-applies

The "AI generated" PR label is now applied automatically by GitHub
Actions to any PR whose title starts with [AI], so the manual "add
this label" instruction is stale. It was also misleading for outside
contributors, who cannot apply labels on PRs against this repo
regardless.

Updated the canonical rules file, the committing-actual-changes
skill, and the review-actual-pr code-review rubric to describe the
prefix as the single trigger and note that the label follows
automatically.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Update Claude Code skills description

Simplified the description of Claude Code skills.

* [AI] Allow cat and mv in PR-review skill's tool allowlist

The workflow saves the final report via `cat > review.md <<'EOF'`
(step 6) and rotates a stale prior report via `mv` (step 2,
re-runs), but the allowed-tools line did not permit either, so
those commands would prompt or fail at runtime. Add Bash(cat:*) and
Bash(mv:*) — keeping the allowlist tight rather than broadening to
Bash(*), so unrelated shell commands still require explicit
authorization.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/agents/pr-and-commit-rules.md

@@ -46,9 +46,7 @@ Before committing, ensure all of the following:
 - `[AI] Add support for new transaction categories`
 - `Fix type error in account validation` (MISSING PREFIX - NOT ALLOWED)
 
-### Labels
-
-Add the **"AI generated"** label to all AI-created pull requests. This helps maintainers understand the nature of the contribution.
+The `"AI generated"` label is applied automatically to any PR whose title starts with `[AI]`, so there is nothing extra to do — and outside contributors cannot apply labels anyway.
 
 ### PR Template: Do Not Fill In
 
@@ -65,6 +63,5 @@ Follow these steps when committing and creating PRs:
 4. Run relevant tests (`yarn test` for all, or workspace-specific)
 5. Stage files and commit with `[AI]` prefix — do not skip hooks
 6. When creating a PR:
-   - Use `[AI]` prefix in the title
-   - Add the `"AI generated"` label
+   - Use `[AI]` prefix in the title (the `"AI generated"` label is auto-applied based on this prefix)
    - Leave the PR template blank (do not fill it in)