test(worker): Stopwatch + reconcile — fill gaps + lifecycle test

Fill the Stopwatch domain to 100% coverage (Stopwatch.tsx + stopwatch.ts,
both now 100% stmts/branch/funcs/lines) and add the reconcile lifecycle test.

New tests cover: idle display-tap start (and no-op without a handling),
pair-count stepper floor + free-typed entry (non-positive ignored), clearing
the handling via the empty option, stop/discard onSuccess reset, discard
arm-window expiry, clearing a pending discard timer on reconcile and on
unmount, and the reconcile lifecycle — running locally, then a poll without
the local session resets the timer and shows the admin-stopped notice.

No behaviour changes. Five defensive/unreachable guards in Stopwatch.tsx are
annotated /* c8 ignore next -- <reason> */ (comment-only): the
paused_seconds ?? 0 coalesce (contract types it non-null) and the early-return
guards in handleSelectZool/handleStart/handleStop/handleDiscard (each triggered
by a control disabled or unrendered in that state).

No bugs found.

apps/worker/src/screens/Stopwatch.test.tsx

@@ -1,4 +1,4 @@
-import { render, screen, waitFor } from '@testing-library/react';
+import { act, fireEvent, render, screen, waitFor } from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
@@ -296,4 +296,197 @@ describe('Stopwatch', () => {
     );
     expect(screen.queryByRole('button', { name: 'Stop & Opslaan' })).not.toBeInTheDocument();
   });
+
+  it('starts by tapping the display when idle and a handling is chosen', async () => {
+    const user = userEvent.setup();
+    renderStopwatch();
+
+    await user.selectOptions(screen.getByLabelText('Type handeling'), 'Frezen');
+    await user.click(screen.getByRole('button', { name: 'Stopwatch' }));
+
+    expect(startMutate).toHaveBeenCalledTimes(1);
+  });
+
+  it('does not start on a display tap when idle with no handling chosen', async () => {
+    const user = userEvent.setup();
+    renderStopwatch();
+
+    await user.click(screen.getByRole('button', { name: 'Stopwatch' }));
+
+    expect(startMutate).not.toHaveBeenCalled();
+  });
+
+  it('decrements the pair count and disables the minus button at the floor of 1', async () => {
+    const user = userEvent.setup();
+    renderStopwatch();
+
+    const input = screen.getByLabelText('Aantal zolen');
+    expect(input).toHaveValue('2');
+
+    await user.click(screen.getByRole('button', { name: 'Minder zolen' }));
+    expect(input).toHaveValue('1');
+    expect(screen.getByRole('button', { name: 'Minder zolen' })).toBeDisabled();
+  });
+
+  it('accepts a free-typed pair count and ignores a non-positive value', async () => {
+    const user = userEvent.setup();
+    renderStopwatch();
+
+    const input = screen.getByLabelText('Aantal zolen');
+    await user.clear(input);
+    await user.type(input, '7');
+    expect(input).toHaveValue('7');
+
+    // A non-positive entry is mirrored in the field but is not adopted as the count.
+    await user.clear(input);
+    await user.type(input, '0');
+    expect(input).toHaveValue('0');
+
+    // Starting uses the last valid count (7), proving the '0' was ignored.
+    await user.selectOptions(screen.getByLabelText('Type handeling'), 'Frezen');
+    await user.click(screen.getByRole('button', { name: 'Start Stopwatch' }));
+    expect(startMutate.mock.calls[0][0]).toMatchObject({ pair_count: 7 });
+  });
+
+  it('clears the chosen handling when the empty option is reselected', async () => {
+    const user = userEvent.setup();
+    renderStopwatch();
+
+    const select = screen.getByLabelText('Type handeling');
+    await user.selectOptions(select, 'Frezen');
+    expect(screen.getByRole('button', { name: 'Start Stopwatch' })).toBeEnabled();
+
+    await user.selectOptions(select, '');
+    expect(screen.getByRole('button', { name: 'Start Stopwatch' })).toBeDisabled();
+  });
+
+  it('resets to idle when stop succeeds', async () => {
+    const user = userEvent.setup();
+    stopMutate.mockImplementation((_id: number, opts?: { onSuccess?: () => void }) => {
+      opts?.onSuccess?.();
+    });
+    mockedUseActiveSessions.mockReturnValue(
+      query<ReturnType<typeof useActiveSessions>>([activeSession()]),
+    );
+    renderStopwatch();
+
+    await user.click(await screen.findByRole('button', { name: 'Stop & Opslaan' }));
+
+    expect(await screen.findByRole('button', { name: 'Start Stopwatch' })).toBeInTheDocument();
+    expect(screen.queryByRole('button', { name: 'Stop & Opslaan' })).not.toBeInTheDocument();
+  });
+
+  it('resets to idle when discard is confirmed and succeeds', async () => {
+    const user = userEvent.setup();
+    discardMutate.mockImplementation((_id: number, opts?: { onSuccess?: () => void }) => {
+      opts?.onSuccess?.();
+    });
+    mockedUseActiveSessions.mockReturnValue(
+      query<ReturnType<typeof useActiveSessions>>([activeSession()]),
+    );
+    renderStopwatch();
+
+    await user.click(await screen.findByRole('button', { name: 'Annuleren' }));
+    await user.click(screen.getByRole('button', { name: 'Nogmaals tikken ter bevestiging' }));
+
+    expect(discardMutate).toHaveBeenCalledTimes(1);
+    expect(await screen.findByRole('button', { name: 'Start Stopwatch' })).toBeInTheDocument();
+  });
+
+  it('disarms discard after the confirm window expires', () => {
+    // Fake timers + fireEvent (userEvent's internal delays fight the 1s display tick).
+    vi.useFakeTimers();
+    mockedUseActiveSessions.mockReturnValue(
+      query<ReturnType<typeof useActiveSessions>>([activeSession()]),
+    );
+    renderStopwatch();
+
+    fireEvent.click(screen.getByRole('button', { name: 'Annuleren' }));
+    expect(
+      screen.getByRole('button', { name: 'Nogmaals tikken ter bevestiging' }),
+    ).toBeInTheDocument();
+
+    // The 3s arm window lapses without a second tap → discard disarms back to 'Annuleren'.
+    act(() => {
+      vi.advanceTimersByTime(3000);
+    });
+    expect(screen.getByRole('button', { name: 'Annuleren' })).toBeInTheDocument();
+  });
+
+  it('clears a pending discard timer when the session is reconciled away', async () => {
+    const user = userEvent.setup();
+    mockedUseActiveSessions.mockReturnValue(
+      query<ReturnType<typeof useActiveSessions>>([activeSession()]),
+    );
+    const { rerender } = renderStopwatch();
+
+    // Arm discard so a pending timer exists when the reconcile reset fires.
+    await user.click(await screen.findByRole('button', { name: 'Annuleren' }));
+    await screen.findByRole('button', { name: 'Nogmaals tikken ter bevestiging' });
+
+    // Admin stops the session: the poll no longer lists it → resetTimer clears the armed timer.
+    mockedUseActiveSessions.mockReturnValue(query<ReturnType<typeof useActiveSessions>>([]));
+    const queryClient = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+    rerender(
+      <QueryClientProvider client={queryClient}>
+        <Stopwatch />
+      </QueryClientProvider>,
+    );
+
+    expect(
+      await screen.findByText('Deze sessie is door de beheerder gestopt.'),
+    ).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: 'Start Stopwatch' })).toBeInTheDocument();
+  });
+
+  it('clears a pending discard timer on unmount', async () => {
+    const user = userEvent.setup();
+    const clearSpy = vi.spyOn(globalThis, 'clearTimeout');
+    mockedUseActiveSessions.mockReturnValue(
+      query<ReturnType<typeof useActiveSessions>>([activeSession()]),
+    );
+    const { unmount } = renderStopwatch();
+
+    await user.click(await screen.findByRole('button', { name: 'Annuleren' }));
+    clearSpy.mockClear();
+    unmount();
+
+    expect(clearSpy).toHaveBeenCalled();
+  });
+
+  it('lifecycle: running locally, then a poll without the session resets it and shows the admin-stopped notice', async () => {
+    const user = userEvent.setup();
+    const local = activeSession({ id: 42 });
+    startMutate.mockImplementation(
+      (_input: unknown, opts?: { onSuccess?: (s: WorkSession) => void }) => {
+        opts?.onSuccess?.(local);
+      },
+    );
+    // Idle to begin with (no server-active session to adopt).
+    mockedUseActiveSessions.mockReturnValue(query<ReturnType<typeof useActiveSessions>>([]));
+    const { rerender } = renderStopwatch();
+
+    // Start locally → the screen enters the running state from the start mutation's onSuccess.
+    await user.selectOptions(screen.getByLabelText('Type handeling'), 'Frezen');
+    await user.click(screen.getByRole('button', { name: 'Start Stopwatch' }));
+    await screen.findByRole('button', { name: 'Stop & Opslaan' });
+
+    // The active-sessions poll now returns a list WITHOUT our session (only another worker's).
+    mockedUseActiveSessions.mockReturnValue(
+      query<ReturnType<typeof useActiveSessions>>([activeSession({ id: 77, user_id: 'other' })]),
+    );
+    const queryClient = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+    rerender(
+      <QueryClientProvider client={queryClient}>
+        <Stopwatch />
+      </QueryClientProvider>,
+    );
+
+    // The timer resets to idle and the admin-stopped notice shows.
+    expect(
+      await screen.findByText('Deze sessie is door de beheerder gestopt.'),
+    ).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: 'Start Stopwatch' })).toBeInTheDocument();
+    expect(screen.queryByRole('button', { name: 'Stop & Opslaan' })).not.toBeInTheDocument();
+  });
 });