feat(FN-2460): improve merge verification fix observability

- Stream in-merge fix-agent text and tool activity through AgentLogger hooks
- Log deterministic verification reruns with per-attempt context for fix loops
- Expand merger tests to cover fix-loop observability and rerun logging behavior

.planning/test-post-times.txt

@@ -0,0 +1,7 @@
+=== POST-RUN 1 start: 2026-04-24T17:07:07Z ===
+POST-RUN 1 duration=150s exit=0
+=== POST-RUN 2 start: 2026-04-24T17:09:37Z ===
+POST-RUN 2 duration=147s exit=0
+=== POST-RUN 3 start: 2026-04-24T17:12:04Z ===
+POST-RUN 3 duration=141s exit=0
+DONE

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

@@ -2368,7 +2368,14 @@ describe("SettingsModal", () => {
     render(<SettingsModal onClose={onClose} addToast={addToast} />);
     await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
 
-    fireEvent.click(screen.getByText("Notifications"));
+    const notificationsButton = screen.queryByRole("button", { name: /Notifications/ });
+    if (notificationsButton) {
+      fireEvent.click(notificationsButton);
+    } else {
+      // Mobile layout uses the section picker dropdown instead of sidebar buttons.
+      fireEvent.change(screen.getByLabelText("Settings Section"), { target: { value: "notifications" } });
+    }
+
     const checkbox = screen.getByLabelText("Enable ntfy.sh notifications");
     fireEvent.click(checkbox);