Console noise purge: deprecated-API fixes + PixelArtDevControls legacy-Input exception

MenuUi FindAnyObjectByType; GA prefabAssetPath->assetPath x2; Synty sample
FindObjectsByType overload; dead death_b field removed. Real bug caught by
the sweep: the F3 pixel-art toggle used legacy Input.GetKeyDown under
Input System-only handling -> InvalidOperationException every frame in Play.
Suite green (455).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Assets/_Project/Scripts/Client/Debug/PixelArtDevControls.cs

@@ -52,7 +52,8 @@ namespace ProjectM.Client
 
         void Update()
         {
-            if (Input.GetKeyDown(KeyCode.F3))
+            var kb = UnityEngine.InputSystem.Keyboard.current; // legacy Input throws under active Input System handling
+            if (kb != null && kb.f3Key.wasPressedThisFrame)
                 _open = !_open;
         }
 

Assets/_Project/Scripts/Client/UI/MenuUi.cs

@@ -27,7 +27,7 @@ namespace ProjectM.Client
 
         public static void EnsureEventSystem()
         {
-            if (UnityEngine.Object.FindFirstObjectByType<EventSystem>() != null) return;
+            if (UnityEngine.Object.FindAnyObjectByType<EventSystem>() != null) return;
             var go = new GameObject("EventSystem");
             go.AddComponent<EventSystem>();
             go.AddComponent<InputSystemUIInputModule>();