fix(ci): cherry-pick CI cleanup onto staging [skip-regression-check] (#798)

Cherry-pick of #794: remove continue-on-error hack, skip redundant checks
on staging PRs, allow ironclaw-ci[bot] in Claude Code review.

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

.github/workflows/code_style.yml

@@ -1,6 +1,8 @@
 name: Code Style
 on:
   pull_request:
+    branches:
+      - main
 
 jobs:
   format: