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]>

docs/architecture/platform-architecture.md

@@ -602,9 +602,11 @@ durations when motion is reduced — in CSS alone, so the Dashboard and every mo
 operating system live; the host chooses an explicit appearance through a small controller, applied
 before React renders. Contrast is tested for every pairing the elements use, in both schemes
 ([ADR 0060](decisions/0060-light-dark-system-theme-and-motion.md)). Settings is one host-owned
-hierarchy in the same sidebar: a landing page, the platform's General, Branding, Displays, Discover
-(module lifecycle: Browse, Installed, Updates), and System, and each module's settings at
-`/settings/<module-id>`. Which of them a person sees is evaluated by the server
+hierarchy in the same sidebar: a landing page that summarises the installation, the platform's
+General, Branding, Displays (where display screens are paired and revoked), Discover (module
+lifecycle: Discover's own page at `/settings/discover`, with Installed and Updates beneath it), and
+System, and each module's settings at `/settings/<module-id>`; the sidebar itself is navigation only
+([ADR 0064](decisions/0064-stage-1-shell-review-corrections.md)). Which of them a person sees is evaluated by the server
 (`GET /api/v1/dashboard/settings`) as presentation hints, while every route behind them keeps its own
 enforcement; the Settings section names are reserved module ids
 ([ADR 0061](decisions/0061-settings-hierarchy-and-module-settings-routes.md)). Personal configuration