Function apply_rewind 

pub fn apply_rewind(
    repo: &ShadowRepo,
    log_path: &Path,
    plan: &RewindPlan,
    force: bool,
) -> Result<RewindResult>

Apply a rewind plan: restore files, then truncate the checkpoint log. Transcript truncation is left to the caller because it owns transcript.jsonl.

force = false aborts on detected conflicts and returns Err(Error::Tool { ... }) whose message lists each file. Callers can choose to retry with force = true.