* feat(commands): add handoffs support for speckit compatibility
- Upgrade frontmatter parser to use js-yaml for complex YAML support
- Add HandoffDefinition interface for speckit-style workflow transitions
- Update CommandFrontmatter and CommandDefinition to include handoffs
- Add comprehensive tests for backward compatibility and complex YAML
- Fix type parameters in auto-slash-command and slashcommand tools
Closes#407
* fix(frontmatter): use JSON_SCHEMA for security and add extra fields tolerance tests
- Use JSON_SCHEMA in yaml.load() to prevent code execution via YAML tags
- Add tests to verify extra fields in frontmatter don't cause failures
- Address Greptile security review comment
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Co-authored-by: sisyphus-dev-ai <sisyphus-dev-ai@users.noreply.github.com>