e2e: migrate remaining specs to event-based waits

[intendednull]

Tracks migration of the 7 remaining Playwright spec files from time-based
to event-based waits. Spec: docs/specs/2026-04-27-event-based-waits-design.md.

Sunset: 2026-09-30. After this date the ratchet script flips to
hard-fail at 0 waitForTimeout calls.

• e2e/permissions.spec.ts
• e2e/mobile.spec.ts
• e2e/mobile-actions.spec.ts
• e2e/multi-peer-mobile.spec.ts
• e2e/cross-browser-sync.spec.ts
• e2e/join-links.spec.ts
• e2e/worker-nodes.spec.ts