fix: Chats doesn't sync for multi client users

server/CONTEXT.md

@@ -48,6 +48,7 @@ Owns the shared, internet-reachable runtime: HTTP routes for server directory /
 
 - Every database schema change ships as a TypeORM **migration**; the live database is never mutated outside the migration system.
 - WebSocket **Envelope** types are defined once in `src/websocket/types.ts` and **must** stay structurally compatible with `toju-app/src/app/shared-kernel/signaling-contracts.ts` — drift between the two is a wire-protocol break.
+- WebSocket messages from a single connection are processed **strictly in arrival order** (`handleWebSocketMessage` chains them per connection id). Concurrent handling lets a `join_server` overtake a still-awaiting `identify` and silently drop room membership.
 - User-supplied URLs are **never** fetched without going through `ssrf-guard.ts`.
 - Secrets (klipy API key, OAuth tokens, signing keys) live in `data/variables.json` or environment variables — never in code, never in logs.