- Prevent server-side exceptions (Application error) on mobile after redirects
- useOneShotSlowHint: guard document; use global setTimeout; conditionally attach visibilitychange
- useConnectionFeedback: guard document.visibilityState; register/remove listeners only on client
- usePageSetup: guard window before tracking referrer and parsing roomId
- tracking: early return when window is undefined
- docs(flows): add “SSR & DOM access guard (must-read)” checklist; renumber next section