Room channel: other T5DE users' community products on their avatars

The proxy follows the client's IMQ chat subscriptions and tells the hub which chats it's in (and the room, from
chat.getOrMakeChat). For the other T5DE users the hub says are in a chat, it gives the client the community
products it has packs for, as *use and *remove lines from them, and adds them to the whole outfits they send.
It also takes community products out of the outfit the client posts to IMVU's chat participant endpoint, which
had been sending them to IMVU.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

cmd/t5de-proxy/main.go

@@ -136,6 +136,7 @@ func run(logger *log.Logger, listen, ready string, parentPID int, trace bool, pa
 		client := hub.New(filepath.Join(data, "hub.json"), saved, logger)
 		if prods != nil {
 			prods.Observer = client
+			client.OnChat = prods.Others
 		}
 		go client.Run(context.Background())
 	} else if !errors.Is(err, hub.ErrSignedOut) {