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/products.md

@@ -99,3 +99,20 @@ every 10 minutes, 20 at a time.
   From there it's served like any pack.
 - Products others wear in a room that it doesn't have are fetched the same way, then given to the client.
 - Library products appear in the client's inventory (see the proxy's README).
+
+## Decorations
+
+T5 furniture and pose products placed in an ordinary IMVU room (design.md, "Decorations over IMVU rooms"). IMVU
+keeps the room without them; the hub keeps them (`room_decoration`, routes in api.md), and only T5DE users see them.
+
+- **Saving**: when the room's owner saves the room (`test.setRoomState`) or the client broadcasts a furniture change
+  in it, the proxy takes the hub products out before it goes to IMVU, and `PUT /api/v1/decorations/<instance>` the
+  room's full list of them (`[furniture instance ID, hub product ID, placement]`).
+- **Loading**: when the client loads an IMVU room (`test.getRoomState`), the proxy `GET`s its decorations and adds
+  them to the room's contents (as local IDs, fetching the products as for outfits); the `hash` tells it whether
+  what it has is current. In the room, an incoming furniture broadcast from IMVU gets the decorations added back
+  the same way.
+- **Changes**: after a `PUT`, every proxy with a chat in that room gets `{"type": "decor", "room": instance}` on the
+  realtime connection and `GET`s again.
+- Viewers only get products they may see: registered, with a revision that isn't retracted, adult ones only for
+  adult accounts. Furniture instance IDs are the proxy's to choose; they must not clash with IMVU's in that room.