Function reparse_impl 

pub async fn reparse_impl(
    store: &Store,
    repo_root: &Path,
    rel_path: &str,
) -> Result<()>

Re-parse a single file and update its store record in place.

Called by:

• mati reparse <path> CLI command
• mati edit-hook <path> (via daemon socket or direct store)
• MCP server socket edit_hook handler

Gracefully degrades on parse failure (P9). Never returns an error for missing files or parse issues — those are logged as warnings.