Add listKeys() and keyCount() helpers across modules (ninth pass).

Standardize key enumeration after size() on map- and registry-style modules, aliasing existing list* methods or primary store keys so callers can inspect occupancy without parsing snapshots.

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

state-crdts/hyper-p2p-crdt-two-phase-set/index.js

@@ -83,6 +83,14 @@ class HyperP2PCrdtTwoPhaseSet extends EventEmitter {
     return s.added.length === 0 && s.removed.length === 0
   }
 
+  listKeys () {
+    return this.elements()
+  }
+
+  keyCount () {
+    return this.size()
+  }
+
   bulkAdd (elements) {
     if (!Array.isArray(elements)) throw new Error('elements array required')
     let n = 0