[Bug]: test.slow(callback) does not extend the timeout of the test it runs in when the callback only uses worker fixtures

Version

1.64.0-next (main @ 07f1a6154); also affects 1.59 through 1.63

Steps to reproduce

playwright.config.ts:

export default { timeout: 1000 };

a.spec.ts (this is the documented form from the test.slow docs, "You can mark all tests in a file or test.describe group as slow ... by passing a callback"):

import { test } from '@playwright/test';

test.slow(({ browserName }) => browserName === 'chromium', 'all tests are slow in chromium');

test('first', async ({}) => {
  console.log('first timeout=' + test.info().timeout);
  await new Promise(r => setTimeout(r, 1500));
});

test('second', async ({}) => {
  console.log('second timeout=' + test.info().timeout);
  await new Promise(r => setTimeout(r, 1500));
});

npx playwright test --workers=1

Expected behavior

Both tests run with a 3000ms timeout and pass.

Actual behavior

first timeout=1000
  1) a.spec.ts:5:5 › first ─── Test timeout of 1000ms exceeded.
second timeout=1000
  2) a.spec.ts:10:5 › second ─ Test timeout of 1000ms exceeded.
  2 failed

The first test never gets the extended timeout. When it fails, the worker restarts, the modifier re-runs for the next test and again does not apply, so every test in the file fails at the base timeout. The same happens with test.slow(() => true).

If the tests do not time out, the second and later tests do get 3000ms (the slow annotation is inherited by subsequent tests in the suite), which hides the problem until a test really needs the extra time.

Additional context

• A modifier callback whose fixtures are all worker-scoped (browserName, or no fixtures at all) is classified as a beforeAll-style hook and runs in its own time slot (workerMain.ts, _runAllHooksForSuite).
• TimeoutManager.slow() triples the currently running slot (this._running.slot) instead of the test's default slot, so the modifier's private slot is tripled and the test's timeout is untouched.
• Since #39596 (test.slow() idempotency, 1.59) the _slow flag is set on that first call, so the inherited annotation or a later test.slow() in the test body is a no-op.

The same mechanism affects test.slow() called from a fixture that has its own { timeout }: the fixture slot is tripled, the test slot is not, and a subsequent test.slow() in the test body silently does nothing.

I intend to work on this and will send a PR.

Environment

- Operating System: macOS (Darwin 25.6.0)
- Node.js: 24.8.0
- Browser: Chromium (bundled r1246)
- Playwright: main @ 07f1a6154