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]>

network-stack/hyper-p2p-overlay-topology/index.js

@@ -104,6 +104,10 @@ class HyperP2POverlayTopology extends EventEmitter {
     return this.snapshot().degree === 0
   }
 
+  size () {
+    return this.snapshot().degree
+  }
+
   getStats () {
     return { ...this._stats, degree: this._neighbors.size, protocol: PROTOCOL }
   }