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/products.go

@@ -48,10 +48,38 @@ type Products struct {
 	// chats it's in (the hub client).
 	Observer Observer
 
+	// Want, if set, is asked for products someone in a room wears that aren't here (the fetcher gets hub products).
+	Want func(id string)
+
 	roomMu sync.Mutex
 	room   room
 }
 
+// Ready is told a product arrived (the fetcher wrote it): it's served from now on, and given to the client for
+// anyone in a room who wears it.
+func (p *Products) Ready(id string) {
+	p.refresh(true)
+	p.roomMu.Lock()
+	p.room.init()
+	var chats []string
+	for chat, avatars := range p.room.last {
+		for _, a := range avatars {
+			for _, it := range a.Items {
+				if it.ID == id {
+					chats = append(chats, chat)
+				}
+			}
+		}
+	}
+	p.roomMu.Unlock()
+	for _, chat := range chats {
+		p.roomMu.Lock()
+		avatars := p.room.last[chat]
+		p.roomMu.Unlock()
+		p.Others(chat, avatars)
+	}
+}
+
 // Observer hears about the client's IMVU account, its community outfit, and the chats it's in.
 type Observer interface {
 	Session(imvuID int64)
@@ -120,7 +148,7 @@ func (p *Products) refresh(force bool) {
 		}
 		for _, e := range entries {
 			dir := filepath.Join(root, e.Name())
-			if !e.IsDir() {
+			if !e.IsDir() || strings.HasPrefix(e.Name(), ".") { // hidden: the fetcher's work in progress
 				continue
 			}
 			if _, err := os.Stat(filepath.Join(dir, "t5de-product.json")); err != nil {