Per Felix's review on issue #496, tests should query observable behaviour via
ARIA roles, not test-only data-testid attributes. Replaces every
'document.querySelector([data-testid=...])' with 'page.getByRole(...)'.
The disabled-button click test uses force: true so Playwright bypasses its
enabled-check — the behaviour under test is precisely that the click is
ignored.
Refs #496.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>