fix(canvas): clear localStoreService singleton on unmount — disposed store was returned to next mount causing currentPageId crash

src/pages/tldraw/singlePlayerPage.tsx

@@ -150,6 +150,7 @@ export default function SinglePlayerPage() {
             snapshotServiceRef.current = null;
             storeRef.current?.dispose();
             storeRef.current = null;
+            localStoreService.clearStore(); // reset singleton so next getStore() creates a fresh store
             setStoreReady(false);
             setCanvasPhase('idle');
         };