Commit Message Writer

Write a git commit message for the following changes.

**Changes:**
{{diff_or_description}}

**Rules:**
- Follow Conventional Commits spec: type(scope): description
- Types: feat, fix, docs, style, refactor, perf, test, chore, ci
- Subject line: max 72 chars, imperative mood, no period
- Body: explain *what* and *why*, not *how* (only if changes are non-trivial)
- Breaking changes: add "BREAKING CHANGE:" footer

Output format:
```
type(scope): subject

[optional body]

[optional footer]
```

Only output the commit message, nothing else.