Get T5 products from the hub's catalogs

The proxy keeps the person's library in a cache folder (hub-products in its data folder), one pack per
product, served like any other pack: the hub says which revision to load and which catalogs host it, each file
comes from a catalog and is checked against the hub's sha256 (files are kept by hash, so a new revision only
downloads what changed), and adult files are fetched with the hub's access token. Products someone wears in a
room that aren't here yet are fetched too, and put on them when they arrive.

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

internal/products/room.go

@@ -30,6 +30,7 @@ type room struct {
 	applied map[string]map[int64][]int64       // chat -> user -> local IDs the client was given for them
 	userIDs map[int64]string                   // user -> the gateway's user_id for them, as last seen
 	missing map[string]bool                    // products others wear that aren't in the packs (logged once)
+	last    map[string][]hub.Avatar            // chat -> what the hub last said about the others in it
 }
 
 func (r *room) init() {
@@ -39,6 +40,7 @@ func (r *room) init() {
 		r.applied = map[string]map[int64][]int64{}
 		r.userIDs = map[int64]string{}
 		r.missing = map[string]bool{}
+		r.last = map[string][]hub.Avatar{}
 	}
 }
 
@@ -184,13 +186,16 @@ func (p *Products) Others(chat string, avatars []hub.Avatar) {
 				locals = append(locals, s.local)
 				continue
 			}
+			if p.Want != nil {
+				p.Want(it.ID) // given to the client when it arrives (Ready)
+			}
 			p.roomMu.Lock()
 			p.room.init()
 			first := !p.room.missing[it.ID]
 			p.room.missing[it.ID] = true
 			p.roomMu.Unlock()
 			if first {
-				p.logf("products: someone in the room wears %q (%s), which isn't in your packs", it.Name, it.ID)
+				p.logf("products: someone in the room wears %q (%s), which isn't here yet", it.Name, it.ID)
 			}
 		}
 		slices.Sort(locals)
@@ -201,9 +206,11 @@ func (p *Products) Others(chat string, avatars []hub.Avatar) {
 	p.room.init()
 	if avatars == nil {
 		delete(p.room.applied, chat)
+		delete(p.room.last, chat)
 		p.roomMu.Unlock()
 		return
 	}
+	p.room.last[chat] = avatars
 	had := p.room.applied[chat]
 	var lines []line
 	for user, old := range had {