Add share pin

tests/hooks/useGame.navigation.test.tsx

@@ -1279,6 +1279,51 @@ describe('OAuth Callback Handling', () => {
   });
 });
 
+describe('/play/:pin URL Join Flow', () => {
+  describe('Landing PIN sync (regression: PIN field empty on /play/:pin)', () => {
+    it('should sync local PIN state when initialPin prop changes after async load', () => {
+      let initialPin: string | null = null;
+      let localPin = initialPin || '';
+      
+      const syncPin = (newInitialPin: string | null) => {
+        if (newInitialPin) {
+          localPin = newInitialPin;
+        }
+      };
+      
+      initialPin = 'TESTPIN';
+      syncPin(initialPin);
+      
+      expect(localPin).toBe('TESTPIN');
+    });
+
+    it('should preserve user-typed PIN when initialPin becomes null', () => {
+      let localPin = 'USER_TYPED';
+      
+      const syncPin = (newInitialPin: string | null) => {
+        if (newInitialPin) {
+          localPin = newInitialPin;
+        }
+      };
+      
+      syncPin(null);
+      
+      expect(localPin).toBe('USER_TYPED');
+    });
+
+    it('should force JOIN mode when initialPin is provided via URL', () => {
+      const getModeFromUrl = (searchParams: URLSearchParams, initialPin?: string): 'HOST' | 'JOIN' => {
+        if (initialPin) return 'JOIN';
+        const modeParam = searchParams.get('mode');
+        return modeParam === 'host' ? 'HOST' : 'JOIN';
+      };
+      
+      const searchParams = new URLSearchParams('?mode=host');
+      expect(getModeFromUrl(searchParams, 'TESTPIN')).toBe('JOIN');
+    });
+  });
+});
+
 describe('State Sync with Async Data Loading', () => {
   describe('Settings modal data sync', () => {
     it('should update editingDefaultConfig when defaultConfig loads', () => {