fix(gateway): align node push token typing and router test mock

src/gateway/server.test.ts

@@ -43,6 +43,12 @@ const mockModelClient = {
     stopReason: 'end_turn',
     usage: { inputTokens: 10, outputTokens: 5 },
   })),
+  setTier: vi.fn(() => true),
+  getTier: vi.fn(() => 'default' as const),
+  getLabel: vi.fn((tier: string) => tier),
+  setTierStrict: vi.fn(),
+  addTierChangeListener: vi.fn(),
+  removeTierChangeListener: vi.fn(),
 };
 
 const mockToolRegistry = {