test(frontend/copilot): extend ChatInput tests to cover model toggle handler

Add describe block for ChatInput model toggle covering:
- render/hide based on feature flag
- standard→advanced and advanced→standard toggle calls
- hide when streaming
- toast notifications for both toggle directions

Also update store mock to use reactive mockCopilotLlmModel variable
and reset it in afterEach for test isolation.

autogpt_platform/frontend/src/app/(platform)/copilot/components/ChatInput/__tests__/ChatInput.test.tsx

@@ -12,12 +12,17 @@ const mockSetCopilotChatMode = vi.fn((mode: string) => {
   mockCopilotMode = mode;
 });
 
+let mockCopilotLlmModel = "standard";
+const mockSetCopilotLlmModel = vi.fn((model: string) => {
+  mockCopilotLlmModel = model;
+});
+
 vi.mock("@/app/(platform)/copilot/store", () => ({
   useCopilotUIStore: () => ({
     copilotChatMode: mockCopilotMode,
     setCopilotChatMode: mockSetCopilotChatMode,
-    copilotLlmModel: "standard",
-    setCopilotLlmModel: vi.fn(),
+    copilotLlmModel: mockCopilotLlmModel,
+    setCopilotLlmModel: mockSetCopilotLlmModel,
     initialPrompt: null,
     setInitialPrompt: vi.fn(),
   }),
@@ -109,6 +114,7 @@ afterEach(() => {
   cleanup();
   vi.clearAllMocks();
   mockCopilotMode = "extended_thinking";
+  mockCopilotLlmModel = "standard";
 });
 
 describe("ChatInput mode toggle", () => {
@@ -189,3 +195,69 @@ describe("ChatInput mode toggle", () => {
     );
   });
 });
+
+describe("ChatInput model toggle", () => {
+  it("renders model toggle button when flag is enabled", () => {
+    mockFlagValue = true;
+    render(<ChatInput onSend={mockOnSend} />);
+    expect(screen.getByLabelText(/switch to advanced model/i)).toBeDefined();
+  });
+
+  it("does not render model toggle when flag is disabled", () => {
+    mockFlagValue = false;
+    render(<ChatInput onSend={mockOnSend} />);
+    expect(
+      screen.queryByLabelText(/switch to (advanced|standard) model/i),
+    ).toBeNull();
+  });
+
+  it("toggles from standard to advanced on click", () => {
+    mockFlagValue = true;
+    mockCopilotLlmModel = "standard";
+    render(<ChatInput onSend={mockOnSend} />);
+    fireEvent.click(screen.getByLabelText(/switch to advanced model/i));
+    expect(mockSetCopilotLlmModel).toHaveBeenCalledWith("advanced");
+  });
+
+  it("toggles from advanced to standard on click", () => {
+    mockFlagValue = true;
+    mockCopilotLlmModel = "advanced";
+    render(<ChatInput onSend={mockOnSend} />);
+    fireEvent.click(screen.getByLabelText(/switch to standard model/i));
+    expect(mockSetCopilotLlmModel).toHaveBeenCalledWith("standard");
+  });
+
+  it("hides model toggle when streaming", () => {
+    mockFlagValue = true;
+    render(<ChatInput onSend={mockOnSend} isStreaming />);
+    expect(
+      screen.queryByLabelText(/switch to (advanced|standard) model/i),
+    ).toBeNull();
+  });
+
+  it("shows a toast when switching to advanced", async () => {
+    const { toast } = await import("@/components/molecules/Toast/use-toast");
+    mockFlagValue = true;
+    mockCopilotLlmModel = "standard";
+    render(<ChatInput onSend={mockOnSend} />);
+    fireEvent.click(screen.getByLabelText(/switch to advanced model/i));
+    expect(toast).toHaveBeenCalledWith(
+      expect.objectContaining({
+        title: expect.stringMatching(/switched to advanced model/i),
+      }),
+    );
+  });
+
+  it("shows a toast when switching to standard", async () => {
+    const { toast } = await import("@/components/molecules/Toast/use-toast");
+    mockFlagValue = true;
+    mockCopilotLlmModel = "advanced";
+    render(<ChatInput onSend={mockOnSend} />);
+    fireEvent.click(screen.getByLabelText(/switch to standard model/i));
+    expect(toast).toHaveBeenCalledWith(
+      expect.objectContaining({
+        title: expect.stringMatching(/switched to standard model/i),
+      }),
+    );
+  });
+});