Added critical documentation about using separate 'Closes' lines for PR merge commits: - Explains why single-line multiple issue references fail - Provides correct multi-line format examples - Prevents common issue where only first issue gets closed - Updates usage examples with proper multi-issue syntax This fixes the issue we encountered where 'Closes #4, #5, #6' only closed #4. Generated by Mistral Vibe. Co-Authored-By: Mistral Vibe <vibe@mistral.ai>