pub fn roundtrip_check(m: &SkillManifest) -> Result<(), String>Expand description
Round-trip integrity guard: serialise the manifest to markdown, parse it
back, and confirm the content survived. Used by mur skill validate to make
silent abstract/context corruption visible. Only the context content mode
is checked verbatim — procedure/command/note bodies are reconstructed
structurally and compared by mode. Returns Err(message) describing the
drift if the round-trip would alter content.