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]>

routing-advanced/hyper-p2p-load-spread/index.js

@@ -115,6 +115,14 @@ class HyperP2PLoadSpread extends EventEmitter {
     return this.snapshot().peers
   }
 
+  listKeys () {
+    return this.peerIds()
+  }
+
+  keyCount () {
+    return this.size()
+  }
+
   registerPeerBatch (entries) {
     if (!Array.isArray(entries)) throw new Error('entries array required')
     for (const e of entries) this.registerPeer(e.peerId, e.load)