Add i18n foundation and translations (#1027)

* feat: add i18n foundation

* feat: localize sessions sidebar

* Localize multirun/scheduled tasks and fix dialog dropdown interactions

* localize git sidebar surface and add zh-CN keys

* feat(ui): localize context panel, diff/plan views, and context sidebar content

* fix(config): resolve user config home via fs/home before embedded home

* localize header/chat UI and complete model/worktree panel strings

* localize worktree + github issue/pr dialog flows

* localize settings sections and split settings i18n dictionaries

* localize additional settings sections and sidebars

* localize more settings pages and dialogs

* fix settings select trigger localization

* localize tunnel settings ui surface

* localize additional settings sections

* localize keyboard shortcuts labels in settings

* localize terminal and utility dialogs surfaces

* feat(i18n): localize remaining UI strings

* Add Ukrainian locale

* Add Spanish locale

* Add Brazilian Portuguese locale

* Polish locale translations

packages/ui/src/components/multirun/AgentSelector.tsx

@@ -9,6 +9,7 @@ import {
 } from '@/components/ui/select';
 import { cn } from '@/lib/utils';
 import { useConfigStore } from '@/stores/useConfigStore';
+import { useI18n } from '@/lib/i18n';
 
 export interface AgentSelectorProps {
   /** Currently selected agent name (empty string for no agent) */
@@ -34,6 +35,7 @@ export const AgentSelector: React.FC<AgentSelectorProps> = ({
   disabled,
   id,
 }) => {
+  const { t } = useI18n();
   const getVisibleAgents = useConfigStore((state) => state.getVisibleAgents);
   const loadAgents = useConfigStore((state) => state.loadAgents);
   const defaultAgentName = useConfigStore((state) => state.currentAgentName);
@@ -91,7 +93,7 @@ export const AgentSelector: React.FC<AgentSelectorProps> = ({
           className,
         )}
       >
-        <SelectValue placeholder="Select an agent" />
+        <SelectValue placeholder={t('multirun.agentSelector.placeholder')} />
       </SelectTrigger>
       <SelectContent fitContent>
         {selectableAgents.length > 0 && (