feat(gui): settings panel with locale and theme preferences

Add the browser Settings surface as slot-composed plugins over new
preference services:

- Rename dsh-client-i18n to dsh-client-locale (locale is the domain
  name); LocaleService adds getLocale()/setLocale(id), immutable
  snapshots, a locale/change event, and dsh.locale persistence.
- ThemeService owns the light/dark/system preference (default system),
  resolves system via prefers-color-scheme, publishes theme/change
  snapshots, persists dsh.theme, and no longer touches the DOM;
  ui-layout's ThemePresenter applies resolved snapshots
  (body[data-ds-dark-theme] + alias tokens) and cleans up on dispose.
- ui-sidebar drops the phase-1 settings dropdown/modal; the foot renders
  the new sidebar.settings slot with the column state.
- New ui-settings shell occupies sidebar.settings: foot trigger row and
  the centered 1080x700 panel (figma 501:29947) with 24% mask, close
  button / mask click / Escape all closing, and a 188px nav projected
  from the settings.section list slot it declares. Nav labels are
  registrant-localized; sections re-register on locale change, so the
  ledger version is the shell's only subscription.
- ui-settings-general registers the General section: Permission and
  Tool Call skeletons, live Language (locale menu) and Appearance
  (Light/Dark/System cubes following the persisted preference); its
  slot store mirrors both service snapshots via apply-side listeners.
- ui-settings-models registers the Models nav entry with an empty
  content column.
- Portaled menus pin z-index above modal overlays (a menu anchored
  inside the settings dialog rendered underneath it and was
  unclickable).
- theme/data/list-pen icons in ui-primitives; settings copy ships as
  zh/en dictionaries; fixture manifests gain the settings rows.

apps/web/tests/session-title.snapshot.ts

@@ -10,9 +10,12 @@ const PLUGINS: readonly (WebBootEntry & { dir: string })[] = [
   { id: '@deepseek-ai/dsh-client-connection', dir: 'connection', url: '/plugins/connection.js', rev: 'fx', inject: [], immediately: true },
   { id: '@deepseek-ai/dsh-client-runtime', dir: 'runtime', url: '/plugins/runtime.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-connection'], immediately: true },
   { id: '@deepseek-ai/dsh-client-ui-theme', dir: 'ui-theme', url: '/plugins/ui-theme.js', rev: 'fx', inject: [], immediately: true },
-  { id: '@deepseek-ai/dsh-client-i18n', dir: 'i18n', url: '/plugins/i18n.js', rev: 'fx', inject: [], immediately: true },
+  { id: '@deepseek-ai/dsh-client-locale', dir: 'locale', url: '/plugins/locale.js', rev: 'fx', inject: [], immediately: true },
   { id: '@deepseek-ai/dsh-client-ui-layout', dir: 'ui-layout', url: '/plugins/ui-layout.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-runtime'] },
   { id: '@deepseek-ai/dsh-client-ui-sidebar', dir: 'ui-sidebar', url: '/plugins/ui-sidebar.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-layout'] },
+  { id: '@deepseek-ai/dsh-client-ui-settings', dir: 'ui-settings', url: '/plugins/ui-settings.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-sidebar', '@deepseek-ai/dsh-client-locale'] },
+  { id: '@deepseek-ai/dsh-client-ui-settings-general', dir: 'ui-settings-general', url: '/plugins/ui-settings-general.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-settings'] },
+  { id: '@deepseek-ai/dsh-client-ui-settings-models', dir: 'ui-settings-models', url: '/plugins/ui-settings-models.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-settings'] },
   { id: '@deepseek-ai/dsh-client-ui-conversation', dir: 'ui-conversation', url: '/plugins/ui-conversation.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-layout'] },
   { id: '@deepseek-ai/dsh-client-ui-workspace', dir: 'ui-workspace', url: '/plugins/ui-workspace.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-runtime', '@deepseek-ai/dsh-client-ui-conversation', '@deepseek-ai/dsh-client-ui-sidebar'] },
   { id: '@deepseek-ai/dsh-client-ui-trajectory', dir: 'ui-trajectory', url: '/plugins/ui-trajectory.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-conversation'] },

apps/web/tests/smoke-real.e2e.ts

@@ -147,7 +147,7 @@ async function detailsTrack(page: Page): Promise<number> {
 // Readiness gate: `dsh web` serves ALL nine manifest plugins; until every UI
 // plugin's client bundle exists and exports apply, the loader fail-louds and
 // the frame never appears.
-const UI_PLUGIN_DIRS = ['connection', 'runtime', 'ui-theme', 'i18n', 'ui-layout', 'ui-sidebar', 'ui-conversation', 'ui-question', 'ui-trajectory']
+const UI_PLUGIN_DIRS = ['connection', 'runtime', 'ui-theme', 'locale', 'ui-layout', 'ui-sidebar', 'ui-conversation', 'ui-question', 'ui-trajectory']
 const ROUND_DONE_MARKER = 'WEB_ROUND_DONE'
 const notReady = UI_PLUGIN_DIRS.filter((dir) => {
   const bundle = join(REPO_ROOT, 'packages/client', dir, 'lib/client.js')

apps/web/tests/workspace-flow.snapshot.ts

@@ -10,9 +10,12 @@ const PLUGINS: readonly (WebBootEntry & { dir: string })[] = [
   { id: '@deepseek-ai/dsh-client-connection', dir: 'connection', url: '/plugins/connection.js', rev: 'fx', inject: [], immediately: true },
   { id: '@deepseek-ai/dsh-client-runtime', dir: 'runtime', url: '/plugins/runtime.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-connection'], immediately: true },
   { id: '@deepseek-ai/dsh-client-ui-theme', dir: 'ui-theme', url: '/plugins/ui-theme.js', rev: 'fx', inject: [], immediately: true },
-  { id: '@deepseek-ai/dsh-client-i18n', dir: 'i18n', url: '/plugins/i18n.js', rev: 'fx', inject: [], immediately: true },
+  { id: '@deepseek-ai/dsh-client-locale', dir: 'locale', url: '/plugins/locale.js', rev: 'fx', inject: [], immediately: true },
   { id: '@deepseek-ai/dsh-client-ui-layout', dir: 'ui-layout', url: '/plugins/ui-layout.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-runtime'] },
   { id: '@deepseek-ai/dsh-client-ui-sidebar', dir: 'ui-sidebar', url: '/plugins/ui-sidebar.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-layout'] },
+  { id: '@deepseek-ai/dsh-client-ui-settings', dir: 'ui-settings', url: '/plugins/ui-settings.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-sidebar', '@deepseek-ai/dsh-client-locale'] },
+  { id: '@deepseek-ai/dsh-client-ui-settings-general', dir: 'ui-settings-general', url: '/plugins/ui-settings-general.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-settings'] },
+  { id: '@deepseek-ai/dsh-client-ui-settings-models', dir: 'ui-settings-models', url: '/plugins/ui-settings-models.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-settings'] },
   { id: '@deepseek-ai/dsh-client-ui-conversation', dir: 'ui-conversation', url: '/plugins/ui-conversation.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-layout'] },
   {
     id: '@deepseek-ai/dsh-client-ui-workspace',