feat(FN-1736): add projectId scoping to chat session creation

- Add projectId field to chat session creation for multi-project isolation
- Include projectId in session response when projectId query param is provided
- Resolve agent from project-scoped store using getProjectContext
- Add projectId assertion to chat session creation tests
- Mock project-store-resolver in tests for proper store isolation
- Update project memory with multi-project scoping audit findings

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

@@ -155,6 +155,13 @@ vi.mock("../mission-interview.js", () => {
   };
 });
 
+// Mock project-store-resolver.js
+const mockGetOrCreateProjectStore = vi.fn();
+vi.mock("../project-store-resolver.js", () => ({
+  getOrCreateProjectStore: mockGetOrCreateProjectStore,
+  invalidateAllGlobalSettingsCaches: vi.fn(),
+}));
+
 // ── Mock Store ──────────────────────────────────────────────────────────────
 
 class MockStore extends EventEmitter {
@@ -272,6 +279,9 @@ describe("Chat API Routes", () => {
     mockChatStore = mockChatStoreInstance;
     mockChatManager = createMockChatManager();
 
+    // Setup project-store-resolver mock to return the mock store
+    mockGetOrCreateProjectStore.mockResolvedValue(store);
+
     const { createServer } = await import("../server.js");
     app = createServer(store as any, {
       chatStore: mockChatStore as any,