Command-owned structured metadata for CLI documentation

Always define canonical examples in CommandDocumentation.examples and compound positional syntax in the first customUsage entry. Chose structured metadata over handwritten or reverse-parsed Markdown because duplicate authorities drift. Preserve these as __examples and __primaryUsage; introspection must expose __primaryUsage as the sole positional row’s public syntax, so help, parent route help, generated docs, skills, and argument tables render the same canonical grammar instead of raw parser placeholders.