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]>

cmd/t5de-proxy/main.go

@@ -33,6 +33,7 @@ import (
 	"time"
 
 	"git.t5de.dev/t5de/t5de-proxy/internal/buildinfo"
+	"git.t5de.dev/t5de/t5de-proxy/internal/fetch"
 	"git.t5de.dev/t5de/t5de-proxy/internal/hub"
 	"git.t5de.dev/t5de/t5de-proxy/internal/parent"
 	"git.t5de.dev/t5de/t5de-proxy/internal/products"
@@ -125,7 +126,12 @@ func run(logger *log.Logger, listen, ready string, parentPID int, trace bool, pa
 		}()
 	}
 	handler := &proxy.Server{Token: token, Log: logger, Trace: trace}
-	prods, err := products.New(packs, data, logger.Printf)
+	// Products from the hub's catalogs are kept as packs in their own folder, served like the others.
+	hubProducts := filepath.Join(data, "hub-products")
+	if err := os.MkdirAll(hubProducts, 0o755); err != nil {
+		logger.Printf("hub products: %v", err)
+	}
+	prods, err := products.New(append(packs, hubProducts), data, logger.Printf)
 	if err != nil {
 		logger.Printf("community products are off: %v", err)
 	} else {
@@ -134,10 +140,14 @@ func run(logger *log.Logger, listen, ready string, parentPID int, trace bool, pa
 	}
 	if saved, err := hub.Load(filepath.Join(data, "hub.json")); err == nil {
 		client := hub.New(filepath.Join(data, "hub.json"), saved, logger)
+		fetcher := fetch.New(client, hubProducts, logger.Printf)
 		if prods != nil {
 			prods.Observer = client
 			client.OnChat = prods.Others
+			fetcher.OnReady = prods.Ready
+			prods.Want = fetcher.Want
 		}
+		client.OnLibrary = func() { fetcher.SyncLibrary(context.Background()) }
 		go client.Run(context.Background())
 	} else if !errors.Is(err, hub.ErrSignedOut) {
 		logger.Printf("hub: %v", err)