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/stores/session-events.ts

@@ -34,6 +34,7 @@ import { createClientSession, mapSdkSessionStatus, type Session, type SessionSta
 import { sessions, setSessions, syncInstanceSessionIndicator, withSession } from "./session-state"
 import { normalizeMessagePart } from "./message-v2/normalizers"
 import { updateSessionInfo } from "./message-v2/session-info"
+import { tGlobal } from "../lib/i18n"
 
 import { loadMessages } from "./session-api"
 import {
@@ -308,7 +309,7 @@ function handleSessionUpdate(instanceId: string, event: EventSessionUpdated): vo
     const newSession = {
       id: info.id,
       instanceId,
-      title: info.title || "Untitled",
+      title: info.title || tGlobal("sessionList.session.untitled"),
       parentId: info.parentID || null,
       agent: "",
       model: {
@@ -415,10 +416,11 @@ function handleSessionCompacted(instanceId: string, event: EventSessionCompacted
   const label = session?.title?.trim() ? session.title : sessionID
   const instanceFolder = instances().get(instanceId)?.folder ?? instanceId
   const instanceName = instanceFolder.split(/[\\/]/).filter(Boolean).pop() ?? instanceFolder
+  const displayLabel = label ? `"${label}"` : sessionID
 
   showToastNotification({
     title: instanceName,
-    message: `Session ${label ? `"${label}"` : sessionID} was compacted`,
+    message: tGlobal("sessionEvents.sessionCompactedToast", { label: displayLabel }),
     variant: "info",
     duration: 10000,
   })
@@ -428,7 +430,7 @@ function handleSessionError(_instanceId: string, event: EventSessionError): void
   const error = event.properties?.error
   log.error(`[SSE] Session error:`, error)
 
-  let message = "Unknown error"
+  let message = tGlobal("sessionEvents.sessionError.unknown")
 
   if (error) {
     if ("data" in error && error.data && typeof error.data === "object" && "message" in error.data) {
@@ -438,8 +440,8 @@ function handleSessionError(_instanceId: string, event: EventSessionError): void
     }
   }
 
-  showAlertDialog(`Error: ${message}`, {
-    title: "Session error",
+  showAlertDialog(tGlobal("sessionEvents.sessionError.message", { message }), {
+    title: tGlobal("sessionEvents.sessionError.title"),
     variant: "error",
   })
 }