fix(world): wrap stage and player in suspense to prevent scene remount

Late asset loads inside GameStageContent (e.g. EbikeSpeedometer's
useTexture) and the spawn-player block were bubbling Suspense up to the
root boundary in pages/page.tsx, which unmounted World mid-load and
triggered a redundant octree rebuild + shadow re-config. Localize the
suspension by wrapping each block in its own Suspense fallback.

Also mount DebugOctreeVisualization conditionally on the new debug
toggle.

src/world/World.tsx

@@ -9,12 +9,16 @@ import { useCameraMode } from "@/hooks/debug/useCameraMode";
 import { useEnvironmentDebug } from "@/hooks/debug/useEnvironmentDebug";
 import { useMapPerformanceDebug } from "@/hooks/debug/useMapPerformanceDebug";
 import { useCharacterDebug } from "@/hooks/debug/useCharacterDebug";
+import { useDebugVisualsDebug } from "@/hooks/debug/useDebugVisualsDebug";
 import { useSceneMode } from "@/hooks/debug/useSceneMode";
 import { useHandTrackingSnapshot } from "@/hooks/handTracking/useHandTrackingSnapshot";
 import { useWorldSceneLoading } from "@/hooks/world/useWorldSceneLoading";
 import { useGameStore } from "@/managers/stores/useGameStore";
+import { useDebugVisualsStore } from "@/managers/stores/useDebugVisualsStore";
 import { DebugCameraControls } from "@/components/debug/scene/DebugCameraControls";
 import { DebugHelpers } from "@/components/debug/scene/DebugHelpers";
+import { DebugOctreeVisualization } from "@/components/debug/DebugOctreeVisualization";
+import { DebugPlayerModel } from "@/components/debug/DebugPlayerModel";
 import { HandTrackingGlove } from "@/components/three/handTracking/HandTrackingGlove";
 import { Environment } from "@/world/Environment";
 import { GameCinematics } from "@/world/GameCinematics";
@@ -36,10 +40,15 @@ export function World({ onLoadingStateChange }: WorldProps): React.JSX.Element {
   useEnvironmentDebug();
   useMapPerformanceDebug();
   useCharacterDebug();
+  useDebugVisualsDebug();
 
   const cameraMode = useCameraMode();
   const sceneMode = useSceneMode();
   const mainState = useGameStore((state) => state.mainState);
+  const showDebugPlayerModel = useDebugVisualsStore(
+    (state) => state.showPlayerModel,
+  );
+  const showDebugOctree = useDebugVisualsStore((state) => state.showOctree);
   const { status, usageStatus } = useHandTrackingSnapshot();
   const {
     octree,
@@ -48,9 +57,6 @@ export function World({ onLoadingStateChange }: WorldProps): React.JSX.Element {
     handleGameStageLoaded,
     handleGameMapLoaded,
     handleOctreeReady,
-    handleShadowWarmupReady,
-    handleShadowWarmupStarted,
-    shouldWarmUpShadows,
   } = useWorldSceneLoading({ sceneMode, onLoadingStateChange });
   const playerSpawnPosition =
     sceneMode === "game"
@@ -65,15 +71,15 @@ export function World({ onLoadingStateChange }: WorldProps): React.JSX.Element {
 
   return (
     <>
-      <Environment
-        shadowWarmup={{
-          active: shouldWarmUpShadows,
-          onReady: handleShadowWarmupReady,
-          onStarted: handleShadowWarmupStarted,
-        }}
-      />
+      <Environment />
       <Lighting />
       <DebugHelpers />
+      {showDebugOctree ? <DebugOctreeVisualization octree={octree} /> : null}
+      {showDebugPlayerModel ? (
+        <Suspense fallback={null}>
+          <DebugPlayerModel />
+        </Suspense>
+      ) : null}
       {showHandTrackingGloves ? (
         <Suspense fallback={null}>
           <HandTrackingGlove handedness="left" />
@@ -92,11 +98,13 @@ export function World({ onLoadingStateChange }: WorldProps): React.JSX.Element {
           {showGameStage ? (
             <Physics>
               <GameStageLoaded onLoaded={handleGameStageLoaded} />
-              <GameStageContent />
+              <Suspense fallback={null}>
+                <GameStageContent />
+              </Suspense>
             </Physics>
           ) : null}
           {spawnPlayer ? (
-            <>
+            <Suspense fallback={null}>
               <GameMusic />
               {mainState === "outro" ? <GameCinematics /> : null}
               {mainState !== "intro" ? <GameDialogues /> : null}
@@ -105,7 +113,7 @@ export function World({ onLoadingStateChange }: WorldProps): React.JSX.Element {
                 octree={octree}
                 spawnPosition={playerSpawnPosition}
               />
-            </>
+            </Suspense>
           ) : null}
         </>
       ) : (