Bring the desktop's session reconnection UX to mobile:
- Warm-cache fast-path: switchSession paints the cached Room transcript
immediately instead of blanking the screen, then refreshes from the
server in parallel (stale cache can't clobber a fresher server page)
- Bounded auto-retry: a failed session.resume (WS reject or REST
transcript failure) retries with exponential backoff 1s->2s->4s->8s,
capped at 4 attempts; WS + REST failures in the same cycle count as one
- Explicit error recovery: after exhaustion the chat shows an error card
with a manual Retry instead of latching the spinner forever; manual
retry resets the backoff cycle
- Reconnect-aware resume: gateway (re)connect clears stale error state
and re-resumes the current session on the new socket
- Unit tests: warm-cache paint, bounded retry exhaustion, WS+REST
dedupe, manual retry reset, reconnect restart
Co-authored-by: M57 <hy4ri@users.noreply.github.com>
