feat(ci): add PR review job and commit-capable mention bot

Rename claude-issue-bot.yml to claude-bot.yml and broaden it beyond
issues:

- handle-pr: review pull requests on open (read diff, label, post one
  grounded review comment); review-only, no code changes.
- mention: allow committing. Add Edit/Write and git tools, contents:
  write, and instruct it to make the smallest correct change and commit
  to the current branch only on an explicit code-change request. Kept
  default user gating (no allowed_non_write_users) so only write-access
  users can trigger commits.
- Refresh the repository map (add internal/eventbus and the
  service/email subpackage) across all three prompts.
- Raise max-turns.
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