feat: align mini chat draft layout

Centers the welcome prompt in mini chat drafts
Keeps the mini chat composer at the bottom
Preserves the standard desktop draft layout

packages/ui/src/components/chat/ChatContainer.tsx

@@ -15,6 +15,7 @@ import { useChatAutoFollow, type AnimationHandlers, type ContentChangeReason } f
 import { useChatTimelineController } from './hooks/useChatTimelineController';
 import { TimelineDialog } from './TimelineDialog';
 import { useChatTurnNavigation } from './hooks/useChatTurnNavigation';
+import { useChatSurfaceMode } from './useChatSurfaceMode';
 import { useDeviceInfo } from '@/lib/device';
 import { Button } from '@/components/ui/button';
 import { OverlayScrollbar } from '@/components/ui/OverlayScrollbar';
@@ -529,9 +530,10 @@ export const ChatContainer: React.FC<ChatContainerProps> = ({ autoOpenDraft = tr
 
     const { isMobile } = useDeviceInfo();
     const isVSCode = isVSCodeRuntime();
+    const chatSurfaceMode = useChatSurfaceMode();
     const draftOpen = Boolean(newSessionDraft?.open);
     const isDesktopExpandedInput = isExpandedInput && !isMobile;
-    const useCompactDraftLayout = isMobile || isVSCode;
+    const useCompactDraftLayout = isMobile || isVSCode || chatSurfaceMode === 'mini-chat';
     const messageListRef = React.useRef<MessageListHandle | null>(null);
     const draftProjectLabel = React.useMemo(() => {
         const selectedProject = newSessionDraft?.selectedProjectId