Decorations over IMVU rooms: the hub's side

T5 products placed in ordinary IMVU rooms, kept per room instance
(room_decoration, migration 0006). GET /api/v1/decorations/:instance (and
?instances= for up to 20) gives what the viewer may see, with a hash;
PUT is for the room owner's T5DE person only, checks the products exist,
and tells every realtime session with a chat in that room ({"type":
"decor"}). Hosted rooms' IDs are refused.

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

docs/design.md

@@ -287,8 +287,8 @@ is per person, shared across their accounts.
 
 ## Rooms (**Decided**: both)
 
-- **Decorations over IMVU rooms**: community furniture placed in an IMVU room, seen only by T5DE users. Placements
-  travel on the room channel like outfits.
+- **Decorations over IMVU rooms**: community furniture placed in an IMVU room, seen only by T5DE users. The hub keeps
+  them per room; proxies strip them from what IMVU gets and add them back on load (products.md, "Decorations").
 - **T5DE-hosted rooms**: the room lives on the hub: scene, furniture placement, owner, moderators, permissions,
   bans, chat, seats, presence. The proxy routes that room's IMQ traffic to the hub, which speaks the subset of
   IMQ the client needs (subscribe, state changes, mounts, messages) and the room-joining XML-RPC calls, so the