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]>

consensus-coordination/hyper-p2p-causal-consensus/index.js

@@ -445,6 +445,10 @@ class HyperP2PCausalConsensus extends EventEmitter {
     return this.snapshot()
   }
 
+  isEmpty () {
+    return this.proposals.size === 0 && this.decidedOrders.size === 0
+  }
+
   async proposeBatch (entries) {
     if (!Array.isArray(entries)) throw new Error('entries array required')
     const out = []