tools: add claude PR reviews

[pzmarzly]

This GitHub CI workflow will automatically run Claude bot over all opened and updated PRs.

See pzmarzly/demo--claude-bot-reviews repo and pzmarzly/demo--claude-bot-reviews#6

Replaces #422

[pzmarzly]

GH Action is green this time, but prints this warning:

Attempt 2 failed: Workflow validation failed. The workflow file must exist and have identical content to the version on the repository's default branch. If you're seeing this on a PR when you first add a code review workflow file to your repository, this is normal and you should ignore this error.
Action skipped due to workflow validation error. This is expected when adding Claude Code workflows to new repositories or on PRs with workflow changes. If you're seeing this, your workflow will begin working once you merge your PR.

[qdeslandes]

Good for me, thanks!