Add isEmpty() helpers across all modules with clearable state.

Seventh expansion pass: domain-specific isEmpty() after moduleSnapshot on every module that has clearAll(), using existing count/snapshot helpers (async variants for temporal, spatial, semantic-vector, and reactive-state indexes).

Co-authored-by: Cursor <[email protected]>

storage-hyperdrive/hyper-p2p-drive-mirror-sync/index.js

@@ -116,6 +116,11 @@ class HyperP2PDriveMirrorSync extends EventEmitter {
     return this.snapshot()
   }
 
+  isEmpty () {
+    const s = this.snapshot()
+    return s.pending === 0 && s.tracked === 0
+  }
+
   getStats () {
     return driveStats(this._stats, PROTOCOL, {
       pending: this._queue.length,