Address PR Comments

Review and address comments on PRs. Supports multiple PRs in parallel using git worktrees.

Usage

/comments                # Current PR
/comments 123            # Single PR
/comments 123 456 789    # Multiple PRs in parallel worktrees

PR DETECTION (when no arguments)

# Check if current branch has open PR
CURRENT_PR=$(gh pr view --json number --jq '.number' 2>/dev/null)