## Summary
- Adds concurrency block to the claude-pr-review workflow
- When a new push is made to a PR, any in-progress review workflow for
that PR is automatically cancelled
- Avoids wasting resources reviewing outdated code

## Test plan
- [ ] Push multiple commits in quick succession to a PR and verify only
the latest run completes

#skip-bugbot

<!-- This is an auto-generated description by cubic. -->
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## Summary by cubic
Add GitHub Actions concurrency to the claude-pr-review workflow so only
the latest run per PR executes. New pushes automatically cancel any
in-progress review, avoiding outdated reviews and saving CI resources.

<sup>Written for commit 8a0a3d25f25657ed9fc34580b7cb51feb43a2c9c.
Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>