Add size() cardinality helper across modules (eighth pass).

Standardize a size() method after isEmpty() on every module with clearAll(), delegating to domain counts or snapshot fields so callers can query occupancy without parsing snapshots.

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

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

@@ -111,6 +111,10 @@ class HyperP2PLoadSpread extends EventEmitter {
     return this.snapshot().peers === 0
   }
 
+  size () {
+    return this.snapshot().peers
+  }
+
   registerPeerBatch (entries) {
     if (!Array.isArray(entries)) throw new Error('entries array required')
     for (const e of entries) this.registerPeer(e.peerId, e.load)