Sign in to T5DE's hub and report presence and community outfits

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

README.md

@@ -54,6 +54,13 @@ products with the outfit they were saved with, and adds them back when the clien
 Requests it changes are re-signed (`X-imvu-auth`) with the session key from the login response, which never
 leaves the machine.
 
+## The hub
+
+`t5de-proxy signin [-hub URL]` signs the proxy in to T5DE's hub (git.t5de.dev/t5de/t5de-hub): it shows a code to
+enter on the hub's website (`/device`) and saves the sign-in in `%APPDATA%\T5DE\proxy\hub.json`, the refresh
+token encrypted for the Windows user (DPAPI). From then on the running proxy keeps a WebSocket to the hub
+(`internal/hub`), reporting which IMVU account the client signed in as and the community products it wears.
+
 ## Building
 
     go test ./...