chore(ai): 🙈 gitignore bonsai output artifacts (#165)

## Summary

Add `ai/out/` to `.gitignore` to exclude ephemeral bonsai check outputs
(`ai-check.json`, `patch-plan.json`) from version control.

## Test plan

- [ ] Verify `ai/out/` no longer appears in `git status`
- [ ] Confirm existing tracked files are unaffected

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: justapithecus

.gitignore

@@ -17,3 +17,6 @@ bench-*.txt
 /stream_write_records
 /vector_artifacts
 /volume_sparse
+
+# Bonsai check output (ephemeral)
+ai/out/