Hygiene B4d: PlayerResolve dedup + explicit Temp-ECB Dispose tail

- New Server/PlayerResolve.TryResolve single-sources the RPC
  SourceConnection -> NetworkId -> conn->player map resolve (3 sites:
  ClassSelectReceive, PrepPurchase, DebugCommandReceive); EntityManager
  reads keep it source-gen-safe from Bursted receivers.
- ecb.Dispose() after Playback in 9 Temp-ECB systems (explicit-lifetime
  hygiene).
- The TuningConfig.GetOrDefault(ref state) variant of this tail was
  REVERTED: state.GetEntityQuery in OnUpdate trips the Entities
  "creates a query during OnUpdate" diagnostic per system per world
  (caught in Play smoke) - the SystemAPI.TryGetSingleton idiom is
  already source-gen-optimal, confirming the original B4 deferral.

Verified: 466/466 EditMode green on the final tree, console clean,
Play smoke 0 errors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/_Project/Scripts/Server/Combat/ClassSelectReceiveSystem.cs

@@ -48,8 +48,7 @@ namespace ProjectM.Server
                 if (!accept) continue;
 
                 var conn = receive.ValueRO.SourceConnection;
-                if (!SystemAPI.HasComponent<NetworkId>(conn)
-                    || !playerByConn.TryGetValue(SystemAPI.GetComponent<NetworkId>(conn).Value, out var player))
+                if (!PlayerResolve.TryResolve(ref state, playerByConn, conn, out var player))
                     continue;
                 if (!SystemAPI.HasComponent<AbilityRef>(player)) continue;