fix(handtracking): reduce GPU pressure on WebGL context loss

Several mitigations against the WebGL context lost that fires when
hand tracking starts on a loaded scene:

- Canvas: fixed DPR [1,1], antialias off, scoped id="game-canvas",
  context-lost handler releases MediaPipe and logs GPU memory counters
- optimizeGLTFScene: cap anisotropy at 2 and stop forcing mipmaps /
  needsUpdate on every pass — avoids massive texture re-uploads
- MediaPipe: force CPU delegate (HAND_TRACKING_BROWSER_DELEGATE),
  cache the landmarker instance, and expose releaseBrowserHandLandmarker
- useBrowserHandTracking / useRemoteHandTracking: idempotent cleanup
  guarded by a cleanedUp flag, try/catch around the detect loop, and
  release of the landmarker on stop
- World: mount HandTrackingGlove only when the matching hand is
  actually present in the snapshot (status connected + hands.length > 0)
- HandTrackingGlove: drop the eager useGLTF.preload that was running
  at startup whether or not hand tracking was used

Does not yet absorb the React StrictMode double-mount — that is the
follow-up commit.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/world/World.tsx

@@ -31,11 +31,20 @@ import { CharacterSystem } from "@/world/characters/CharacterSystem";
 import { Player } from "@/world/player/Player";
 import { TestMap } from "@/world/debug/TestMap";
 import type { SceneLoadingChangeHandler } from "@/types/world/sceneLoading";
+import type { HandTrackingGloveHandedness } from "@/hooks/handTracking/useHandTrackingGloveStatus";
+import type { HandTrackingHand } from "@/types/handTracking/handTracking";
 
 interface WorldProps {
   onLoadingStateChange?: SceneLoadingChangeHandler | undefined;
 }
 
+function hasTrackedHand(
+  hands: HandTrackingHand[],
+  handedness: HandTrackingGloveHandedness,
+): boolean {
+  return hands.some((hand) => hand.handedness.toLowerCase() === handedness);
+}
+
 export function World({ onLoadingStateChange }: WorldProps): React.JSX.Element {
   useEnvironmentDebug();
   useMapPerformanceDebug();
@@ -49,7 +58,7 @@ export function World({ onLoadingStateChange }: WorldProps): React.JSX.Element {
     (state) => state.showPlayerModel,
   );
   const showDebugOctree = useDebugVisualsStore((state) => state.showOctree);
-  const { status, usageStatus } = useHandTrackingSnapshot();
+  const { hands, status, usageStatus } = useHandTrackingSnapshot();
   const {
     octree,
     gameplayReady,
@@ -63,8 +72,11 @@ export function World({ onLoadingStateChange }: WorldProps): React.JSX.Element {
       ? PLAYER_SPAWN_POSITION_GAME
       : PLAYER_SPAWN_POSITION_PHYSICS;
   const showHandTrackingGloves =
-    sceneMode === "physics" ||
-    (status !== "idle" && usageStatus !== "inactive");
+    status === "connected" && usageStatus !== "inactive" && hands.length > 0;
+  const showLeftHandTrackingGlove =
+    showHandTrackingGloves && hasTrackedHand(hands, "left");
+  const showRightHandTrackingGlove =
+    showHandTrackingGloves && hasTrackedHand(hands, "right");
   const spawnPlayer =
     cameraMode !== "debug" &&
     (sceneMode === "game" ? gameplayReady : octree !== null);
@@ -82,8 +94,12 @@ export function World({ onLoadingStateChange }: WorldProps): React.JSX.Element {
       ) : null}
       {showHandTrackingGloves ? (
         <Suspense fallback={null}>
-          <HandTrackingGlove handedness="left" />
-          <HandTrackingGlove handedness="right" />
+          {showLeftHandTrackingGlove ? (
+            <HandTrackingGlove handedness="left" />
+          ) : null}
+          {showRightHandTrackingGlove ? (
+            <HandTrackingGlove handedness="right" />
+          ) : null}
         </Suspense>
       ) : null}
       {cameraMode === "debug" ? <DebugCameraControls /> : null}