feat: Add native GitHub issue-branch linking and closingIssuesReferences fallback

[sylvansys]

Summary

• Add hook script for native GitHub branch-issue linking using createLinkedBranch mutation
• Add closingIssuesReferences GraphQL fallback to requirements-reviewer
• Configure SessionStart hook in settings.json

Changes

New: .claude/hooks/link-branch-to-issue.sh

Hook script that:

• Uses GitHub's native createLinkedBranch mutation for new branches (creates proper "Development" section link)
• Falls back to local tracking when branch already exists on remote
• Updates .claude/logs/branch-issues.json as a cache

Updated: .github/actions/requirements-reviewer/action.yml

Added third fallback for issue detection:

1. Branch name parsing (123-feature → #123)
2. PR body keywords (Closes #X, Fixes #X, Resolves #X)
3. New: GitHub's closingIssuesReferences GraphQL API

Updated: .claude/settings.json

Added SessionStart hook configuration to run the link script when ISSUE_NUMBER is provided.

Why This Matters

• Resolves namespace collision between issues and PRs (e.g., branch 51-something could mean issue docs: Update CLAUDE.md with auto-setup guide #51 or PR docs: Update CLAUDE.md with auto-setup guide #51)
• Uses GitHub's native Development section for proper issue-branch linking
• Provides multiple fallback methods for requirements-reviewer to find linked issues

Closes #52

Test plan

• Verify hook script syntax with bash -n
• Test hook script manually with existing branch (falls back correctly)
• Test with new branch creation (uses createLinkedBranch)
• Create test PR to verify closingIssuesReferences fallback

🤖 Generated with Claude Code