* [web] add external 15s heartbeat to socket.io connection
* [web] extend debugging context for client errors
- include performance.now() timestamp for correlating other timings
- include connectionState, especially for new externalHeartbeat detail
- include spellCheckLanguage to check on client-side spelling impact
* [web] remove unnecessary hook dependency
Co-authored-by: Alf Eaton <alf.eaton@overleaf.com>
* Refactor externalHeartbeat
* Add connectionManager to context
* Clear the interval earlier, and on connect
* [web] refactor handling of socket debugging info
* [web] add split-test for external socket heartbeat
* [web] fully remove connectionManager from connection context
---------
Co-authored-by: Alf Eaton <alf.eaton@overleaf.com>
GitOrigin-RevId: fbebe64f8aa207eb4fd4a8f27d522d1cac35f9d4
