Design: T5 products in the client's shop and inventory

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

docs/design.md

@@ -234,6 +234,19 @@ number, `productdata/<id>/<revision>/`) but hardly shows them; T5DE shows them o
 - **Seeing versus wearing** (**Decided**): anyone can *see* any catalog's products on someone else (subject to their
   own age settings); getting and wearing them needs membership where the catalog requires it.
 
+## In the client's shop and inventory (planned, the user's goal)
+
+- **"Buying" is saving**: getting a T5 product (free) adds it to the person's library on the hub. The proxy shows
+  library products in the client's own inventory, next to IMVU's, so they're worn like any other.
+- **Browsing in the shop**: T5 products appear in the client's shop, with a T5 filter beside IMVU's rating filter
+  and a T5 badge on T5 products (inventory, shop, product cards). Images are drawn and kept for this (the user's
+  Pictures\T5DE badges, made by its `draw.py`): badges 18x14, 25x21 and 23x19; filter strips for IMVU's two
+  layouts with T5 added last (`GA|all|AP|T5`, `GA|AP|AP+|all|T5`) and `all|T5` for people without Access Pass,
+  who get no rating filter today (T5 products aren't only adult ones).
+- Needs: the hub's product registry and catalogs serving files (so products don't have to be local packs), the
+  library on the hub, the proxy answering the inventory's and shop's calls for T5 products, and a patch to the
+  shop page for the filter and badges.
+
 ## Outfits
 
 1. The user puts on a community item. The client shows it (proxy answers for it); the patch sends IMVU the outfit