Function sweep_old_transcripts 

pub fn sweep_old_transcripts(
    dir: &Path,
    max_files: usize,
) -> Result<usize, Error>

Delete the oldest .jsonl files in dir when the count exceeds max_files.

Files are sorted by modification time (oldest first). Returns the number of files deleted.

Errors

Returns io::Error if the directory cannot be read or a file cannot be deleted.