feat(chat): confirm before deleting a message

Use the existing styledConfirm modal before destructive chat message deletion so accidental clicks can be cancelled.

static/js/chat.js

@@ -4481,6 +4481,15 @@ import { wireArrowUpRecall, getLastUserMessageFromChatHistory } from './composer
    * Delete an AI message and its preceding user message from the conversation.
    */
   export async function deleteMessage(msgElement) {
+    if (uiModule && uiModule.styledConfirm) {
+      const ok = await uiModule.styledConfirm('Delete this message?', {
+        confirmText: 'Delete',
+        cancelText: 'Cancel',
+        danger: true,
+      });
+      if (!ok) return;
+    }
+
     const box = document.getElementById('chat-history');
     const allMsgs = Array.from(box.querySelectorAll('.msg'));
     const clickedIndex = allMsgs.indexOf(msgElement);