docs(app): what signing out and deleting the account show meanwhile, and on failure

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyon_app/README.md

@@ -51,7 +51,12 @@ Written as the apps are: Dart 3.13's primary constructors, Material from
 - **The account** (`AccountTiles`): whose account on which instance,
   switching to the account on another, signing out (which of an anonymous
   account deletes it, so asks first) and deleting it (after asking), for an
-  app's settings, in the app's words where only it can say them.
+  app's settings, in the app's words where only it can say them. While one
+  runs, the person's app stays and its tile shows a spinner; one that fails
+  keeps them signed in and says why once, in a snack bar (in a sheet, give
+  it `hasSnackBars`). An instance out of reach signs out on the device all
+  the same (Serverpod's `signOutDevice`), so only the device's own storage
+  fails a sign-out.
 - **Signing in** (`lib/src/auth/`): `AuthRepository` on an `AuthGateway`;
   `ServerpodAuthGateway` signs in anonymously and with GitHub (the system
   browser and a loopback address on Linux and Windows, `LoopbackWebAuth`),