feat(ui): localize UI strings

Converts hardcoded UI copy to i18n keys across the app, adds global translation for non-component modules, and splits the English catalog into feature modules with duplicate-key detection.

packages/ui/src/components/agent-selector.tsx

@@ -3,6 +3,7 @@ import { For, Show, createEffect, createMemo } from "solid-js"
 import { agents, fetchAgents, sessions } from "../stores/sessions"
 import { ChevronDown } from "lucide-solid"
 import type { Agent } from "../types/session"
+import { useI18n } from "../lib/i18n"
 import { getLogger } from "../lib/logger"
 import Kbd from "./kbd"
 const log = getLogger("session")
@@ -16,6 +17,7 @@ interface AgentSelectorProps {
 }
 
 export default function AgentSelector(props: AgentSelectorProps) {
+  const { t } = useI18n()
   const instanceAgents = () => agents().get(props.instanceId) || []
 
   const session = createMemo(() => {
@@ -72,7 +74,7 @@ export default function AgentSelector(props: AgentSelectorProps) {
         options={availableAgents()}
         optionValue="name"
         optionTextValue="name"
-        placeholder="Select agent..."
+        placeholder={t("agentSelector.placeholder")}
         itemComponent={(itemProps) => (
           <Select.Item
             item={itemProps.item}
@@ -82,7 +84,7 @@ export default function AgentSelector(props: AgentSelectorProps) {
               <Select.ItemLabel class="selector-option-label flex items-center gap-2">
                 <span>{itemProps.item.rawValue.name}</span>
                 <Show when={itemProps.item.rawValue.mode === "subagent"}>
-                  <span class="neutral-badge">subagent</span>
+                  <span class="neutral-badge">{t("agentSelector.badge.subagent")}</span>
                 </Show>
               </Select.ItemLabel>
               <Show when={itemProps.item.rawValue.description}>
@@ -105,7 +107,7 @@ export default function AgentSelector(props: AgentSelectorProps) {
               {(state) => (
                 <div class="selector-trigger-label selector-trigger-label--stacked">
                   <span class="selector-trigger-primary selector-trigger-primary--align-left">
-                    Agent: {state.selectedOption()?.name ?? "None"}
+                    {t("agentSelector.trigger.primary", { agent: state.selectedOption()?.name ?? t("agentSelector.none") })}
                   </span>
                 </div>
               )}