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/locale/tests/invariant.spec.ts

@@ -0,0 +1,30 @@
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import { apply as nodeApply } from '@deepseek-ai/dsh-client-locale'
+import { apply as clientApply, COMMON_NS, LocaleService, inject } from '@deepseek-ai/dsh-client-locale/client'
+import * as LocaleInvariant from '@deepseek-ai/dsh-client-locale/invariant'
+import InvariantService from '@deepseek-ai/dsh-invariants'
+
+describe('invariant companion', () => {
+  it('registers under the package name with an empty installer', async () => {
+    const ctx = new Context()
+    await ctx.plugin(InvariantService, { enabled: true })
+    await expect(ctx.plugin(LocaleInvariant).await()).resolves.toBeDefined()
+  })
+
+  it('node-half apply is a no-op host placeholder', () => {
+    nodeApply()
+    expect(true).toBe(true) // reaching here without throw is the contract
+  })
+
+  it('client apply provides ctx.locale seeded with the zh/en common namespace', async () => {
+    expect(inject).toEqual([])
+    const ctx = new Context()
+    await ctx.plugin({ inject, apply: clientApply }).await()
+    const locale = ctx.get('locale')
+    expect(locale).toBeInstanceOf(LocaleService)
+    // Seeded dictionaries occupy the (ns, locale) seats even while empty.
+    expect(() => (locale as LocaleService).register(COMMON_NS, 'zh', {})).toThrow('already has locale')
+    expect(() => (locale as LocaleService).register(COMMON_NS, 'en', {})).toThrow('already has locale')
+  })
+})

packages/client/locale/tests/locale.spec.ts

@@ -0,0 +1,90 @@
+// @vitest-environment jsdom
+import { beforeEach, describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import type { LocaleSnapshot } from '@deepseek-ai/dsh-client-locale/client'
+import { LocaleService, STORAGE_KEY } from '@deepseek-ai/dsh-client-locale/client'
+
+const make = (): { ctx: Context; svc: LocaleService; events: LocaleSnapshot[] } => {
+  const ctx = new Context()
+  const events: LocaleSnapshot[] = []
+  ctx.on('locale/change', (snapshot) => { events.push(snapshot) })
+  return { ctx, svc: new LocaleService(ctx), events }
+}
+
+describe('LocaleService', () => {
+  beforeEach(() => {
+    localStorage.clear()
+  })
+
+  it('translates through the active-locale -> zh -> key chain', () => {
+    const { svc } = make()
+    svc.register('ns', 'zh', { hello: '你好', onlyZh: '仅中文' })
+    svc.register('ns', 'en', { hello: 'Hello' })
+    const t = svc.bind('ns')
+    expect(svc.getLocale().active).toBe('zh')
+    expect(t('hello')).toBe('你好')
+    svc.setLocale('en')
+    expect(t('hello')).toBe('Hello')
+    expect(t('onlyZh')).toBe('仅中文')
+    expect(t('missing.key')).toBe('missing.key')
+  })
+
+  it('interpolates {name} params and leaves unknown placeholders intact', () => {
+    const { svc } = make()
+    svc.register('ns', 'zh', { greet: '你好，{name}！第 {n} 次', partial: '{known} 与 {unknown}' })
+    const t = svc.bind('ns')
+    expect(t('greet', { name: '世界', n: 2 })).toBe('你好，世界！第 2 次')
+    expect(t('partial', { known: 'A' })).toBe('A 与 {unknown}')
+  })
+
+  it('bind returns a stable per-namespace function identity', () => {
+    const { svc } = make()
+    expect(svc.bind('a')).toBe(svc.bind('a'))
+    expect(svc.bind('a')).not.toBe(svc.bind('b'))
+  })
+
+  it('rejects duplicate (ns, locale) and disposer only removes its own dict', () => {
+    const { svc } = make()
+    const dispose = svc.register('ns', 'zh', { k: 'v1' })
+    expect(() => svc.register('ns', 'zh', { k: 'v2' })).toThrow('already has locale')
+    dispose()
+    const t = svc.bind('ns')
+    expect(t('k')).toBe('k')
+    svc.register('ns', 'zh', { k: 'v2' })
+    expect(t('k')).toBe('v2')
+    dispose()
+    expect(t('k')).toBe('v2')
+  })
+
+  it('setLocale persists, republishes an immutable snapshot, and no-ops on same value', () => {
+    const { svc, events } = make()
+    svc.setLocale('en')
+    expect(svc.getLocale().active).toBe('en')
+    expect(localStorage.getItem(STORAGE_KEY)).toBe('en')
+    expect(events).toHaveLength(1)
+    expect(events[0]).toBe(svc.getLocale())
+    expect(events[0]!.revision).toBe(1)
+    svc.setLocale('en')
+    expect(events).toHaveLength(1)
+  })
+
+  it('throws on unknown locale ids', () => {
+    const { svc } = make()
+    expect(() => { svc.setLocale('fr') }).toThrow('not registered')
+  })
+
+  it('restores a persisted locale and falls back to zh on garbage', () => {
+    localStorage.setItem(STORAGE_KEY, 'en')
+    expect(make().svc.getLocale().active).toBe('en')
+    localStorage.setItem(STORAGE_KEY, 'fr')
+    expect(make().svc.getLocale().active).toBe('zh')
+  })
+
+  it('exposes the two shipped locales with self-described labels', () => {
+    const { svc } = make()
+    expect(svc.getLocale().locales).toEqual([
+      { id: 'zh', label: '中文' },
+      { id: 'en', label: 'English' },
+    ])
+  })
+})