port(m1): wave 7h — Unity overloads + SDK return types + RoomRoot:UIBase (56->40)

- Resources.LoadAsync(string) non-generic, LayerMask implicit-from-int, Animation
  string indexer.
- SDK return-type fixes: RedShellSDK.MarkConversion/LogEvent return IEnumerator
  (StartCoroutine arg), Packsize.Test() returns bool (!Test()).
- RoomRoot : UIBase (decomp base) so TopBar/Footer's (RoomRoot) casts succeed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

SVSim.BattleEngine/Shim/External/LooseEnds.cs

@@ -141,8 +141,8 @@ namespace RedShellSDK
         public static void SetApiKey(string apiKey) { }
         public static void SetUserId(string userId) { }
         public static void SetVerboseLogs(bool verbose) { }
-        public static void MarkConversion() { }
-        public static void LogEvent(string type) { }
+        public static System.Collections.IEnumerator MarkConversion() { yield break; }
+        public static System.Collections.IEnumerator LogEvent(string type) { yield break; }
     }
 }
 namespace ZXing

SVSim.BattleEngine/Shim/External/SdkStubs.cs

@@ -97,5 +97,5 @@ namespace BestHTTP.Decompression.Zlib
 
 // Native plugins (no decomp source) referenced unqualified from global scope.
 public static class TimeNativePlugin { public static float GetDeviceOperatingTime() => 0f; }
-public static class Packsize { public static void Test() { } }
+public static class Packsize { public static bool Test() => true; }
 public static class DllCheck { public static bool Test() => true; }