Function enqueue_local 

pub fn enqueue_local(
    store: &Store,
    source: &str,
    _label: &str,
    content_type: &str,
    raw: Vec<u8>,
    byte_size: i64,
) -> Result<String, StoreError>

Persist a clip to the local store with a local-<ULID> id and synced=false, then enforce the offline cap. Returns the temporary id — also used as the relay idempotency_key on flush so the relay can dedup retries.