- frontmatter merge: multi-field merge, conflict overwrite, missing file, invalid JSON - frontmatter validate: all 3 schemas (plan, summary, verification), missing fields detection with count, unknown schema error, missing file error
- frontmatter merge: multi-field merge, conflict overwrite, missing file, invalid JSON - frontmatter validate: all 3 schemas (plan, summary, verification), missing fields detection with count, unknown schema error, missing file error