Chat with a connection still works after you disconnect from them

**What happens:** After you disconnect from (remove) a connection, you can still open the chat conversation with that person and send and receive messages. The chat is not closed when the connection ends. **Expected:** Once you disconnect from someone, chat with them should no longer be available — the existing conversation should be closed/hidden and sending new messages should be blocked. Real-time chat is a connections-only feature. **Where:** Connections / chat (messaging a connection). **Repro:** 1. Connect with another user (become mutual connections). 2. Open the chat with them and send a message to confirm it works. 3. Disconnect / remove that connection. 4. Go back to the chat with the same person. 5. You can still open the conversation and send/receive messages.