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-sidebar/src/client/SidebarRoot.module.css

@@ -49,7 +49,7 @@
 .railIn .iconButton,
 .railIn .newSession,
 .railIn .searchButton,
-.railIn .foot {
+.railIn .footArea {
   animation: rail-in 150ms var(--ds-ease-in-out) 100ms backwards;
 }
 
@@ -372,45 +372,11 @@
   font-size: 13px;
 }
 
-/* Foot: settings entry (figma 133:7668, 49 hug): the former 18/10 vertical
-   margins fold into the row so the hover pill spans the full 49px. */
-.foot {
+/* Foot seat: pure layout — the flex slot pinning the sidebar.settings slot
+   content to the column bottom. Row visuals belong to the slot occupant
+   (ui-settings). */
+.footArea {
   flex: none;
-  display: flex;
-  align-items: center;
-  gap: 8px;
-  height: 49px;
-  margin: 8px 0 0; /* + 49px row + root padBottom 6 keeps the old 57px band */
-  padding: 0 2px 0 6px;
-  border-radius: 12px;
-  cursor: pointer;
-  overflow: hidden;
-  color: var(--dsw-alias-label-primary);
-}
-
-.foot:hover {
-  background: var(--dsw-alias-interactive-bg-hover);
-}
-
-/* Rail settings: the same 36x36 circle box as the other rail controls. */
-.collapsed .foot {
-  width: 36px;
-  height: 36px;
-  margin: 18px 0 10px;
-  justify-content: center;
-  gap: 0;
-  padding: 0;
-  border-radius: 50%;
-}
-
-.footLabel {
-  max-width: 120px;
-  overflow: hidden;
-  white-space: nowrap;
-}
-
-.collapsed .footLabel {
-  max-width: 0;
 }
 
 @media (prefers-reduced-motion: reduce) {
@@ -419,7 +385,7 @@
   .railIn .iconButton,
   .railIn .newSession,
   .railIn .searchButton,
-  .railIn .foot {
+  .railIn .footArea {
     transition: none;
     animation: none;
   }

packages/client/ui-sidebar/src/client/SidebarRoot.tsx

@@ -12,7 +12,7 @@ import clsx from 'clsx'
 import {
   BrandWordmark, FishLogo,
   IconCloseFill14, IconNewChatOutline16, IconPanelLeftOutline16, IconPersonalizationOutline16,
-  IconProjectAddOutline16, IconSearchOutline16, IconSettingsOutline14,
+  IconProjectAddOutline16, IconSearchOutline16,
   Menu, Tooltip,
 } from '@deepseek-ai/dsh-client-ui-primitives'
 import type { WorkspaceView } from '@deepseek-ai/dsh-client-runtime/client'
@@ -314,9 +314,10 @@ export function SidebarRoot({
         )}
       </div>
 
-      <div className={css.foot} role="button" tabIndex={0} aria-label="Settings">
-        <IconSettingsOutline14 size={wide ? 14 : 18} />
-        {wide && <span className={clsx(css.footLabel, css.wide)}>Settings</span>}
+      {/* Foot seat: the flex slot pinning the settings entry to the column
+          bottom; ui-settings occupies it with the trigger row + panel. */}
+      <div className={css.footArea}>
+        {renderSlot('sidebar.settings', { wide })}
       </div>
     </div>
   )

packages/client/ui-sidebar/src/client/contract/slots.ts

@@ -20,9 +20,24 @@ declare module '@deepseek-ai/dsh-client-ui-slots' {
      * is claiming); ui-workspace registers the picker.
      */
     'sidebar.workspace': { kind: 'single'; scope: 'root'; owner: SidebarWorkspaceOwnerProps }
+    /**
+     * The settings seat at the sidebar foot. Declared by this package's
+     * 'sidebar' entry; ui-settings registers its trigger row + modal panel.
+     * The sidebar passes only its column state — it holds no settings state.
+     */
+    'sidebar.settings': { kind: 'single'; scope: 'root'; owner: SidebarSettingsOwnerProps }
   }
 }
 
+/**
+ * Owner share of the sidebar settings seat: the column display state the
+ * occupant's trigger row must render against (wide row vs rail icon).
+ */
+export interface SidebarSettingsOwnerProps {
+  /** Whether the sidebar renders wide content (false = 56px rail). */
+  wide: boolean
+}
+
 /**
  * Owner share of the sidebar workspace hole: popover geometry plus the
  * sidebar's pick semantics. The picked Host Workspace is already real; the
@@ -62,8 +77,9 @@ export type SidebarRootInjected = {
 
 /**
  * Full component props: layout owner state/actions plus global useSessions
- * and useWorkspaces, the declared Workspace picker render share, and this
- * package's injected callback. No store is registered.
+ * and useWorkspaces, the declared child-slot render shares (Workspace picker
+ * and settings seat), and this package's injected callback. No store is
+ * registered.
  */
 export type SidebarRootComponentProps =
-  PropsRuntime<'sidebar'> & PropsRenderSlots<'sidebar.workspace'> & SidebarRootInjected
+  PropsRuntime<'sidebar'> & PropsRenderSlots<'sidebar.workspace' | 'sidebar.settings'> & SidebarRootInjected

packages/client/ui-sidebar/src/client/index.ts

@@ -3,7 +3,7 @@ import type { ClientContext } from '@deepseek-ai/dsh-client-runtime/client'
 import type { SidebarRootInjected } from './contract/slots.ts'
 import { SidebarRoot } from './SidebarRoot.tsx'
 
-export type { SidebarRootComponentProps, SidebarRootInjected, SidebarWorkspaceOwnerProps } from './contract/slots.ts'
+export type { SidebarRootComponentProps, SidebarRootInjected, SidebarSettingsOwnerProps, SidebarWorkspaceOwnerProps } from './contract/slots.ts'
 
 /** Services required by the sidebar plugin. */
 export const inject = ['slots', 'layout', 'sessions', 'workspaces']
@@ -20,9 +20,12 @@ export function apply(ctx: ClientContext): void {
   ctx.effect(
     () => ctx.slots.register({
       name: 'sidebar',
-      // SidebarRoot owns this picker site; ui-workspace registers the shared
-      // picker that selects a Host Workspace for a frontend Session Intent.
-      children: { 'sidebar.workspace': { kind: 'single', scope: 'root' } },
+      // SidebarRoot owns these sites; ui-workspace registers the shared
+      // picker, ui-settings registers the settings trigger + panel.
+      children: {
+        'sidebar.workspace': { kind: 'single', scope: 'root' },
+        'sidebar.settings': { kind: 'single', scope: 'root' },
+      },
       inject: injectProps,
     }, SidebarRoot),
     'ui-sidebar: slot registration',