feat(FN-3466): add mutation coverage for agent view refreshes

Adds deterministic split-pane refresh behavior to the Agents views (AgentsView and AgentDetailView), with comprehensive test coverage for the mutation refreshes in the detail pane and the agents hook.

Fusion-Task-Id: FN-3466

packages/dashboard/app/hooks/__tests__/useAgents.test.ts

@@ -118,6 +118,25 @@ describe("useAgents", () => {
     expect(mockFetchAgents).toHaveBeenLastCalledWith({ state: "active", role: "executor", includeEphemeral: false }, undefined);
   });
 
+  it("refreshAgents reloads both list and stats in one call", async () => {
+    const { result } = renderHook(() => useAgents());
+
+    await waitFor(() => {
+      expect(mockFetchAgents).toHaveBeenCalled();
+      expect(mockFetchAgentStats).toHaveBeenCalled();
+    });
+
+    mockFetchAgents.mockClear();
+    mockFetchAgentStats.mockClear();
+
+    await act(async () => {
+      await result.current.refreshAgents();
+    });
+
+    expect(mockFetchAgents).toHaveBeenCalledTimes(1);
+    expect(mockFetchAgentStats).toHaveBeenCalledTimes(1);
+  });
+
   it("handles fetchAgents rejection gracefully", async () => {
     mockFetchAgents.mockRejectedValueOnce(new Error("agents failed"));