bonk code reviews (#2892)
* Add bonk agent for interactive /bonk mentions and PR review
Set up ask-bonk with Kimi K2.5 via Cloudflare AI Gateway. Interactive
workflow (bonk.yml) triggers on /bonk and @ask-bonk in issue/PR comments.
Auto-review on new PRs (new-pr-review.yml) is disabled for now while
testing. Includes a cog-tailored review prompt in bonk_reviewer.md.
* Add pull_request trigger to bonk for branch testing
* Trigger bonk test run
* Clean up bonk triggers: comment-only interactive, auto-review on PR push
