fix(frontend): align session detail contract in tests

frontend/tests/vertical-slice.test.ts

@@ -16,6 +16,7 @@ function makeApiMock(overrides?: Partial<ApiClient>): ApiClient {
         session: { code: 'ABCD12', status: 'lobby', host_id: 1, current_round: 1, players_count: 3 },
         players: [],
         round_question: null,
+        reveal: null,
         phase_view_model: {
           status: 'lobby',
           round_number: 1,
@@ -56,7 +57,15 @@ function makeApiMock(overrides?: Partial<ApiClient>): ApiClient {
         session: { code: 'ABCD12', status: 'lie', current_round: 1 },
         round: { number: 1, category: { slug: 'history', name: 'History' } }
       }
-    })
+    }),
+    showQuestion: vi.fn(),
+    mixAnswers: vi.fn(),
+    calculateScores: vi.fn(),
+    getScoreboard: vi.fn(),
+    startNextRound: vi.fn(),
+    finishGame: vi.fn(),
+    submitLie: vi.fn(),
+    submitGuess: vi.fn()
   };
 
   return { ...base, ...overrides };