OpenChamber stream bug breaks live updates

Looks like the recent live-stream rewrite shipped a brittle edge case, and the browser freeze is just where it shows up.

• –The `event-pipeline` / `Error in input stream` trace suggests the session stream is dying upstream, so incremental updates never reach the UI.
• –The timing matches OpenChamber's recent release notes, which say v1.9.2 rebuilt live session sync and streaming updates, making a regression plausible.
• –The Windows + Firefox + localhost setup could be exposing an endpoint or transport quirk, but the local config 404s hint there may also be a backend path-resolution issue.
• –If the bug reproduces across restarts, it is likely in the stream lifecycle or server state handling, not cached browser state; a downgrade or browser swap would be the fastest isolation test.