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.

packages/client/ui-layout/tests/apply.spec.ts

@@ -9,6 +9,7 @@
 import { Context } from 'cordis'
 import { describe, expect, it, vi } from 'vitest'
 import { SlotsService } from '@deepseek-ai/dsh-client-runtime/client'
+import { apply as themeApply, inject as themeInject, ThemeService } from '@deepseek-ai/dsh-client-ui-theme/client'
 import { apply, inject, LayoutService } from '@deepseek-ai/dsh-client-ui-layout/client'
 import { apply as nodeApply } from '@deepseek-ai/dsh-client-ui-layout'
 import * as invariant from '@deepseek-ai/dsh-client-ui-layout/invariant'
@@ -16,13 +17,14 @@ import * as invariant from '@deepseek-ai/dsh-client-ui-layout/invariant'
 async function bench() {
   const ctx = new Context()
   const slotsFiber = ctx.plugin(SlotsService)
+  await ctx.plugin({ inject: themeInject, apply: themeApply }).await()
   await slotsFiber.await()
   return { ctx, slots: ctx.get('slots') as SlotsService }
 }
 
 describe('ui-layout client apply', () => {
   it('declares its service dependencies', () => {
-    expect(inject).toEqual(['slots'])
+    expect(inject).toEqual(['slots', 'theme'])
   })
 
   it('provides ctx.layout and registers AppFrame into root with the four child declarations', async () => {
@@ -53,6 +55,23 @@ describe('ui-layout client apply', () => {
     expect(actions.toggleSidebar).toHaveBeenCalledOnce()
   })
 
+  it('theme presenter applies the initial snapshot, follows theme/change, and unwinds on dispose', async () => {
+    const { ctx } = await bench()
+    const fiber = ctx.plugin({ inject: [...inject], apply })
+    await fiber.await()
+    // Initial getter application: jsdom has no matchMedia, system resolves light.
+    expect(document.body.hasAttribute('data-ds-dark-theme')).toBe(false)
+    const theme = ctx.get('theme') as ThemeService
+    theme.setTheme('dark')
+    expect(document.body.hasAttribute('data-ds-dark-theme')).toBe(true)
+    await fiber.dispose()
+    expect(document.body.hasAttribute('data-ds-dark-theme')).toBe(false)
+    // Listener is off: further theme changes no longer reach the body.
+    theme.setTheme('light')
+    theme.setTheme('dark')
+    expect(document.body.hasAttribute('data-ds-dark-theme')).toBe(false)
+  })
+
   it('teardown unwinds the service, the root registration, and the child declarations', async () => {
     const { ctx, slots } = await bench()
     const fiber = ctx.plugin({ inject: [...inject], apply })