fix(frontend): restore default session context store in vertical slice

frontend/tests/vertical-slice.test.ts

@@ -68,11 +68,43 @@ function makeSessionContextStore(initial: SessionContext | null = null): Session
     get: vi.fn(() => value),
     set: vi.fn((next: SessionContext) => {
       value = next;
+      return next;
     })
   };
 }
 
 describe('vertical slice controller: lobby -> join -> start round', () => {
+  it('uses createSessionContextStore by default (no manual injection)', async () => {
+    vi.resetModules();
+    const defaultStore = {
+      get: vi.fn(() => null),
+      set: vi.fn((next: SessionContext) => next),
+      clear: vi.fn()
+    };
+
+    vi.doMock('../src/spa/session-context-store', async () => {
+      const actual = await vi.importActual<typeof import('../src/spa/session-context-store')>('../src/spa/session-context-store');
+      return {
+        ...actual,
+        createSessionContextStore: vi.fn(() => defaultStore)
+      };
+    });
+
+    const { createVerticalSliceController: createControllerWithMock } = await import('../src/spa/vertical-slice');
+    const api = makeApiMock();
+    const controller = createControllerWithMock(api);
+
+    await controller.joinLobby('ABCD12', 'Maja');
+
+    expect(defaultStore.set).toHaveBeenCalledWith({
+      sessionCode: 'ABCD12',
+      playerId: 9,
+      token: 'token-1'
+    });
+
+    vi.doUnmock('../src/spa/session-context-store');
+    vi.resetModules();
+  });
   it('tracks loading and success state for join + start flow', async () => {
     const api = makeApiMock();
     const controller = createVerticalSliceController(api);
@@ -102,8 +134,8 @@ describe('vertical slice controller: lobby -> join -> start round', () => {
 
     expect(sessionContextStore.set).toHaveBeenCalledWith({
       sessionCode: 'ABCD12',
-      playerToken: 'token-1',
-      nickname: 'Maja'
+      playerId: 9,
+      token: 'token-1'
     });
     expect(controller.getState().sessionCode).toBe('ABCD12');
   });
@@ -112,8 +144,8 @@ describe('vertical slice controller: lobby -> join -> start round', () => {
     const api = makeApiMock();
     const sessionContextStore = makeSessionContextStore({
       sessionCode: 'wxyz99',
-      playerToken: 'token-old',
-      nickname: 'Maja'
+      playerId: 5,
+      token: 'token-old'
     });
     const controller = createVerticalSliceController(api, sessionContextStore);