Fix the Stage 1 Dashboard UX defects found in assembled review

The assembled Stage 1 Dashboard was reviewed by hand on a desktop, with
the sidebar collapsed, and on an iPhone. This fixes what that review
found, and records the decisions in ADR 0064:

- Discover is its own page at /settings/discover, with Installed and
  Updates beneath it as children. There is no Browse item any more.
  /settings/discover/browse is still read, as an alias, and is respelled
  in place. Parents and children now read as a hierarchy: a guide line,
  text-only children, a disclosure chevron, and parent and current
  states that look different.
- The sidebar is navigation only. Display pairing moves from the sidebar
  and drawer to Settings -> Displays: the paired displays, a deliberate
  Add display dialog, and revocation. Nothing takes focus on arrival;
  the code field is focused only once Add display is chosen.
- Collapsed icons are centred. Nav-link layout moves from inline styles
  to the shell stylesheet, and every collapsed item is one square
  centred on the rail.
- /settings is an overview of the installation: displays paired,
  modules installed and running, and a line for each other area. It
  reads only existing endpoints.
- Phones get a sticky, safe-area-aware header holding the menu trigger
  and the page name. New pages start at the top, and focus no longer
  scrolls content under the header.
- @ekklesia/ui draws checkbox and radio indicators from tokens rather
  than accent-color, so the selected state is the strong accent in
  Light and Dark alike.

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

surfaces/shell/src/browser/AccountPages.tsx

@@ -195,7 +195,7 @@ function ChoiceGroup<Value extends string>(props: {
             >
               <input
                 checked={checked}
-                className="ek-shell-choice__input ek-focusable"
+                className="ek-radio__input ek-shell-choice__input ek-focusable"
                 name={props.name}
                 onChange={() => props.onChange(option.value)}
                 type="radio"