Function runs_unreadable 

pub fn runs_unreadable(runs: &Path) -> usize

Runs on disk under runs whose state this build cannot parse - almost always a schema bump, occasionally a run killed mid-write.

Exposed so every surface that reports on runs shares one count instead of each re-deriving it: /api/health reports it as runs_unreadable, and magi doctor calls this directly rather than guessing at the same number a second way.