feat(theme): Light/Dark/System, reduced motion, and one radius scale

The theme foundation DESIGN.md requires (ADR 0060):

- A design token may carry a `dark` value and a `reduced` value. The
  token stylesheet selects them in CSS alone: dark under
  prefers-color-scheme unless the host chose light, or when it chose
  dark; motion durations zero under prefers-reduced-motion unless it
  allowed motion, or when it chose reduce. `color-scheme` travels with
  the tokens. System is live, an explicit choice wins, and every module
  root follows through custom-property inheritance, with no module
  contract change.
- @ekklesia/design-tokens adds a small appearance API: system/light/dark
  and system/reduce/allow, parsers for untrusted stored values,
  resolvers, and a controller that applies the attributes immediately.
  The shell applies it before React renders. That is the hook the
  account preferences work will feed; nothing is persisted. The
  Dashboard page declares `color-scheme: light dark` so a dark system
  never flashes white. Displays stay light.
- A designed dark theme: teal-tinted charcoal, never pure black or
  white, the same teal accent.
- WCAG AA contrast is tested for 41 element pairings in both schemes.
  Two light pairings failed and are fixed visibly: text.muted darkens,
  and form controls get a new border.control (3:1).
  background.placeholder keeps skeletons visible in dark.
- Motion tokens (duration-short, duration-ambient) replace literal
  durations and every per-element reduced-motion rule. radius.scale
  multiplies sm/md/lg, unchanged at its default of 1.
- The sign-in card and module loading/error text move from literal
  colours to tokens. Guards keep raw colours and literal radii out of
  Dashboard product source and @ekklesia/ui.
- Fixes ConfirmationDialog's phrase input, which used a class that
  does not exist (`ek-input`) and so was unstyled.

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

surfaces/shell/src/display/main.tsx

@@ -1,4 +1,8 @@
-import { designToken, installEkklesiaDesignTokens } from "@ekklesia/design-tokens";
+import {
+  createEkklesiaThemeController,
+  designToken,
+  installEkklesiaDesignTokens,
+} from "@ekklesia/design-tokens";
 import { EkklesiaUiStyles } from "@ekklesia/ui";
 import { createRoot } from "react-dom/client";
 import type { EkklesiaHostConfig } from "../host-protocol.js";
@@ -52,6 +56,17 @@ try {
  * module's display artifact then inherits the tokens into its isolated root (ADR 0039). */
 installEkklesiaDesignTokens(document);
 
+/**
+ * A display stays light, whatever its operating system prefers (ADR 0060). A screen in a lobby or
+ * a sanctuary is configured once by whoever set it up, not by a person's appearance preference, and
+ * Stage 0 displays must look exactly as they did. Motion still follows the system.
+ */
+createEkklesiaThemeController({
+  appearance: "light",
+  motion: "system",
+  target: document.documentElement,
+});
+
 createRoot(container).render(
   <>
     <EkklesiaUiStyles />