ci: add Claude Code GitHub Actions workflows

Add two workflow configurations for AI-assisted development:
- claude-code-review.yml: Automatic PR reviews on new/updated PRs
- claude.yml: Interactive Claude assistant via @claude mentions

These workflows integrate with Claude Code to automate PR reviews
and provide on-demand AI assistance in issues and PR comments.

🤖 Generated with Claude Code (https://claude.ai/code)
Co-Authored-By: Claude <[email protected]>