FN-6152: reset dashboard route test mocks between cases

Tighten dashboard route tests by resetting shared request and mock state between cases.

- add default request headers and per-test chat SSE mock cleanup to prevent state leakage
- restore mocked globals after GitHub review-refresh and settings route tests
- clear secrets sync remote-fetch mock history before each test run

Files changed:
 packages/dashboard/src/__tests__/chat-routes.test.ts         | 10 ++++++++++
 packages/dashboard/src/__tests__/routes-github.test.ts       |  4 ++++
 packages/dashboard/src/__tests__/routes-secrets-sync.test.ts |  1 +
 packages/dashboard/src/__tests__/routes-settings.test.ts     |  4 ++++
 4 files changed, 19 insertions(+)

Fusion-Task-Id: FN-6152

Fusion-Task-Lineage: c7db7cf2-ea2e-4c76-9fc5-5679cc708fe3

packages/dashboard/src/__tests__/chat-routes.test.ts

@@ -11,6 +11,7 @@ function createSSERequest(): Request {
   const emitter = new EventEmitter();
   emitter.setMaxListeners(50);
   (emitter as any).query = {};  // required: routes read req.query.projectId
+  (emitter as any).headers = {};  // required: routes read req.headers["last-event-id"]
   return emitter as unknown as Request;
 }
 
@@ -1204,6 +1205,15 @@ describe("Chat API Routes", () => {
     });
 
     describe("SSE stream lifecycle", () => {
+      beforeEach(() => {
+        mockSendMessage.mockResolvedValue(undefined);
+        mockChatStreamManager.reset();
+        mockChatStreamManager.getBufferedEvents.mockClear();
+        mockChatStreamManager.subscribe.mockClear();
+        mockChatStreamManager.broadcast.mockClear();
+        mockChatStreamManager.cleanupSession.mockClear();
+      });
+
       /**
        * Helper to invoke the chat SSE route handler directly.
        * Tests the SSE route behavior by calling the handler with mock req/res.

packages/dashboard/src/__tests__/routes-github.test.ts

@@ -2409,6 +2409,10 @@ describe("POST /tasks/:id/review/refresh", () => {
     store = createMockStore();
   });
 
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
   function buildApp() {
     const app = express();
     app.use(express.json());

packages/dashboard/src/__tests__/routes-secrets-sync.test.ts

@@ -50,6 +50,7 @@ describe("routes secrets sync", () => {
 
   beforeEach(async () => {
     vi.restoreAllMocks();
+    mockedFetchFromRemoteNode.mockClear();
     fixture = await createFixture("fn-secrets-sync-");
     secrets = fixture.secretsStore;
 

packages/dashboard/src/__tests__/routes-settings.test.ts

@@ -1141,6 +1141,10 @@ describe("PUT /settings/global", () => {
     store = createMockStore();
   });
 
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
   function buildApp() {
     const app = express();
     app.use(express.json());