Patch Changes

• fix(db): prevent live query from being marked ready before subset data is loaded (#1081)

  In on-demand sync mode, the live query collection was being marked as ready before
  the subset data finished loading. This caused useLiveQuery to return isReady=true
  with empty data, and useLiveSuspenseQuery to release suspense prematurely.

  The root cause was a race condition: the status:change listener in CollectionSubscriber
  was registered after the snapshot was triggered. If loadSubset resolved quickly
  (or synchronously), the loadingSubset status transition would be missed entirely,
  so trackLoadPromise was never called on the live query collection.

  Changes:

  1. Core fix - onStatusChange option: Added onStatusChange callback option to
     subscribeChanges(). The listener is registered BEFORE any snapshot is requested,
     guaranteeing no status transitions are missed. This replaces the error-prone pattern
     of manually deferring snapshots and registering listeners in the correct order.
  2. Ready state gating: updateLiveQueryStatus() now checks isLoadingSubset on the
     live query collection before marking it ready, and listens for loadingSubset:change
     to trigger the ready check when subset loading completes.