docs: add commit hygiene rules to AGENTS.md

- Double-check git status before any commit
- Delete unused/obsolete files when refactoring

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AGENTS.md

@@ -322,6 +322,8 @@ git push origin main
 - Use exact text matching (whitespace matters)
 - Test after every change
 - Run full test suite before committing
+- **Double-check `git status` before ANY commit** - verify staged files match intent
+- **Delete unused/obsolete files** when refactors or feature removals make them irrelevant
 - Update documentation when changing behavior
 - Follow existing code style
 - Use conventional commit messages