feat(FN-3212): remove runtime memory-backend side-load, add regression test

Merged FN-3207, FN-3212, and FN-3242: removed runtime memory-backend side-loading in core, added comprehensive regression tests for QuickChat, chat routes, and SSE streams, and documented compact mobile chat dialogs in the dashboard guide. The refactor in `project-memory.ts` reduces complexity while

Fusion-Task-Id: FN-3212

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

@@ -821,6 +821,42 @@ describe("ChatManager.sendMessage", () => {
     expect(createSpy.mock.calls[0]?.[0]?.sessionManager).toBeDefined();
   });
 
+  it("reopens the same CLI session on second turn and persists both assistant replies", async () => {
+    const promptSpy = vi
+      .fn()
+      .mockResolvedValueOnce(undefined)
+      .mockResolvedValueOnce(undefined);
+
+    mockChatStore.getSession
+      .mockReturnValueOnce({
+        id: "chat-001",
+        agentId: "agent-001",
+        status: "active",
+        cliSessionFile: null,
+      })
+      .mockReturnValueOnce({
+        id: "chat-001",
+        agentId: "agent-001",
+        status: "active",
+        cliSessionFile: __dirname + "/chat-manager.test.ts",
+      });
+
+    __setCreateFnAgent(async () => ({
+      session: { prompt: promptSpy, dispose: vi.fn(), state: { messages: [{ role: "assistant", content: "Done" }] } },
+    }));
+
+    const chatManager = createChatManager();
+    await chatManager.sendMessage("chat-001", "Turn one");
+    await chatManager.sendMessage("chat-001", "Turn two");
+
+    expect(mockSessionManagerCreate).toHaveBeenCalledTimes(1);
+    expect(mockSessionManagerOpen).toHaveBeenCalledTimes(1);
+    expect(promptSpy).toHaveBeenCalledTimes(2);
+
+    const assistantCalls = mockChatStore.addMessage.mock.calls.filter((call) => call[1].role === "assistant");
+    expect(assistantCalls).toHaveLength(2);
+  });
+
   it("reopens the same CLI session on subsequent turns instead of creating a new one", async () => {
     mockChatStore.getSession.mockReturnValue({
       id: "chat-001",

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

@@ -928,6 +928,35 @@ describe("Chat API Routes", () => {
   // ── SSE Streaming Tests ────────────────────────────────────────────────────
 
   describe("POST /api/chat/sessions/:id/messages (SSE)", () => {
+    it("creates a fresh backend send for second turn on same session", async () => {
+      mockGetSession.mockReturnValue(sampleSession);
+      mockSendMessage.mockImplementation(async (sessionId: string) => {
+        mockChatStreamManager.broadcast(sessionId, {
+          type: "done",
+          data: { messageId: `msg-${Date.now()}` },
+        });
+      });
+
+      const first = await request(
+        app,
+        "POST",
+        "/api/chat/sessions/chat-abc123/messages",
+        JSON.stringify({ content: "Turn 1" }),
+        { "content-type": "application/json" },
+      );
+
+      const second = await request(
+        app,
+        "POST",
+        "/api/chat/sessions/chat-abc123/messages",
+        JSON.stringify({ content: "Turn 2" }),
+        { "content-type": "application/json" },
+      );
+
+      expect(first.status).toBe(200);
+      expect(second.status).toBe(200);
+    });
+
     it("returns 404 when session not found", async () => {
       mockGetSession.mockReturnValue(undefined);