feat(FN-2222): move heartbeat multiplier control to Agents screen

- Add heartbeat multiplier global control UI to AgentsView with supporting behavior and tests
- Remove heartbeat multiplier field from Settings modal scheduling section and update related test coverage
- Add mobile-specific CSS adjustments for agent global controls and extend mobile view assertions
- Update docs to reflect the new heartbeat multiplier location in agents and settings references

packages/dashboard/app/components/__tests__/AgentsView.test.tsx

@@ -15,6 +15,8 @@ vi.mock("../../api", () => ({
   deleteAgent: vi.fn(),
   startAgentRun: vi.fn(),
   fetchOrgTree: vi.fn(),
+  fetchSettings: vi.fn().mockResolvedValue({ heartbeatMultiplier: 1 }),
+  updateSettings: vi.fn().mockResolvedValue({}),
   fetchModels: vi.fn().mockResolvedValue({ models: [] }),
   fetchDiscoveredSkills: vi.fn().mockResolvedValue([]),
 }));
@@ -31,6 +33,8 @@ const mockDeleteAgent = vi.mocked(apiModule.deleteAgent);
 const mockStartAgentRun = vi.mocked(apiModule.startAgentRun);
 const mockFetchOrgTree = vi.mocked((apiModule as any).fetchOrgTree);
 const mockFetchAgentStats = vi.mocked((apiModule as any).fetchAgentStats);
+const mockFetchSettings = vi.mocked((apiModule as any).fetchSettings);
+const mockUpdateSettings = vi.mocked((apiModule as any).updateSettings);
 
 describe("AgentsView", () => {
   const mockAddToast = vi.fn();
@@ -95,6 +99,8 @@ describe("AgentsView", () => {
       status: "active",
     });
     mockFetchOrgTree.mockResolvedValue([]);
+    mockFetchSettings.mockResolvedValue({ heartbeatMultiplier: 1 });
+    mockUpdateSettings.mockResolvedValue({});
   });
 
   describe("rendering", () => {
@@ -1443,4 +1449,86 @@ describe("AgentsView", () => {
       });
     });
   });
+
+  describe("global heartbeat multiplier", () => {
+    it("renders the global heartbeat speed control", async () => {
+      mockFetchSettings.mockResolvedValue({ heartbeatMultiplier: 1 });
+      render(<AgentsView addToast={mockAddToast} />);
+
+      await waitFor(() => {
+        expect(screen.getByLabelText("Heartbeat Speed")).toBeTruthy();
+      });
+
+      // Check the slider and preset are rendered
+      expect(screen.getByRole("slider", { name: "Heartbeat Speed" })).toBeTruthy();
+      expect(screen.getByLabelText("Heartbeat speed preset")).toBeTruthy();
+
+      // Check helper text
+      expect(screen.getByText(/Scales all agent heartbeat intervals/)).toBeTruthy();
+    });
+
+    it("loads heartbeat multiplier from settings", async () => {
+      mockFetchSettings.mockResolvedValue({ heartbeatMultiplier: 2.5 });
+      render(<AgentsView addToast={mockAddToast} />);
+
+      await waitFor(() => {
+        const slider = screen.getByRole("slider", { name: "Heartbeat Speed" }) as HTMLInputElement;
+        expect(slider.value).toBe("2.5");
+      });
+    });
+
+    it("saves heartbeat multiplier when slider changes", async () => {
+      mockFetchSettings.mockResolvedValue({ heartbeatMultiplier: 1 });
+      render(<AgentsView addToast={mockAddToast} />);
+
+      await waitFor(() => {
+        expect(screen.getByLabelText("Heartbeat Speed")).toBeTruthy();
+      });
+
+      // Change the slider
+      const slider = screen.getByRole("slider", { name: "Heartbeat Speed" });
+      fireEvent.change(slider, { target: { value: "3" } });
+
+      await waitFor(() => {
+        expect(mockUpdateSettings).toHaveBeenCalledWith({ heartbeatMultiplier: 3 }, undefined);
+        expect(mockAddToast).toHaveBeenCalledWith("Heartbeat speed set to ×3.0", "success");
+      });
+    });
+
+    it("saves heartbeat multiplier when preset is selected", async () => {
+      mockFetchSettings.mockResolvedValue({ heartbeatMultiplier: 1 });
+      render(<AgentsView addToast={mockAddToast} />);
+
+      await waitFor(() => {
+        expect(screen.getByLabelText("Heartbeat Speed")).toBeTruthy();
+      });
+
+      // Change the preset
+      const preset = screen.getByLabelText("Heartbeat speed preset") as HTMLSelectElement;
+      fireEvent.change(preset, { target: { value: "0.5" } });
+
+      await waitFor(() => {
+        expect(mockUpdateSettings).toHaveBeenCalledWith({ heartbeatMultiplier: 0.5 }, undefined);
+      });
+    });
+
+    it("disables control while saving", async () => {
+      mockFetchSettings.mockResolvedValue({ heartbeatMultiplier: 1 });
+      mockUpdateSettings.mockImplementation(() => new Promise(resolve => setTimeout(resolve, 100)));
+      render(<AgentsView addToast={mockAddToast} />);
+
+      await waitFor(() => {
+        expect(screen.getByLabelText("Heartbeat Speed")).toBeTruthy();
+      });
+
+      // Change the slider - this should start the save
+      const slider = screen.getByRole("slider", { name: "Heartbeat Speed" });
+      fireEvent.change(slider, { target: { value: "2" } });
+
+      // Both controls should be disabled while saving
+      await waitFor(() => {
+        expect(slider).toBeDisabled();
+      });
+    });
+  });
 });

packages/dashboard/app/components/__tests__/SettingsModal.test.tsx

@@ -896,45 +896,15 @@ describe("SettingsModal", () => {
     expect(checkbox.getAttribute("type")).toBe("checkbox");
   });
 
-  it("renders heartbeat multiplier slider in Scheduling", async () => {
+  it("does not render heartbeat multiplier control in Scheduling section", async () => {
     render(<SettingsModal onClose={onClose} addToast={addToast} />);
     await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
 
     fireEvent.click(screen.getByText("Scheduling"));
 
-    const slider = screen.getByLabelText("Heartbeat Multiplier") as HTMLInputElement;
-    expect(slider.type).toBe("range");
-    expect(slider.value).toBe("1");
-    expect(screen.getByText("×1.0")).toBeTruthy();
-  });
-
-  it("updates heartbeat multiplier form state when slider changes", async () => {
-    render(<SettingsModal onClose={onClose} addToast={addToast} />);
-    await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
-
-    fireEvent.click(screen.getByText("Scheduling"));
-
-    const slider = screen.getByLabelText("Heartbeat Multiplier") as HTMLInputElement;
-    fireEvent.change(slider, { target: { value: "2.5" } });
-
-    expect(slider.value).toBe("2.5");
-    expect(screen.getByText("×2.5")).toBeTruthy();
-  });
-
-  it("includes heartbeatMultiplier in save payload", async () => {
-    render(<SettingsModal onClose={onClose} addToast={addToast} />);
-    await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
-
-    fireEvent.click(screen.getByText("Scheduling"));
-
-    const slider = screen.getByLabelText("Heartbeat Multiplier") as HTMLInputElement;
-    fireEvent.change(slider, { target: { value: "3" } });
-
-    fireEvent.click(screen.getByText("Save"));
-    await waitFor(() => expect(updateSettings).toHaveBeenCalledTimes(1));
-
-    const payload = (updateSettings as ReturnType<typeof vi.fn>).mock.calls[0][0];
-    expect(payload.heartbeatMultiplier).toBe(3);
+    // Heartbeat multiplier is now configured from the Agents screen, not Settings
+    expect(screen.queryByLabelText("Heartbeat Multiplier")).toBeNull();
+    expect(screen.queryByText(/Heartbeat Multiplier/)).toBeNull();
   });
 
   it("save button calls updateSettings with form data", async () => {

packages/dashboard/app/components/__tests__/agents-view-mobile.test.tsx

@@ -45,6 +45,8 @@ vi.mock("../../api", () => ({
   startAgentRun: vi.fn(),
   fetchModels: vi.fn(() => Promise.resolve({ models: [] })),
   fetchOrgTree: vi.fn(),
+  fetchSettings: vi.fn(() => Promise.resolve({ heartbeatMultiplier: 1 })),
+  updateSettings: vi.fn(() => Promise.resolve({})),
 }));
 
 import {