fix: improve session export and empty chat states

Move session export into the sidebar menu
Add desktop save-and-reveal flow for exported markdown
Show empty-state UI instead of a loading skeleton for empty sessions

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

@@ -1,11 +1,9 @@
 import React from 'react';
-import { RiArrowLeftLine, RiDownloadLine } from '@remixicon/react';
+import { RiArrowLeftLine } from '@remixicon/react';
 import type { Message, Part, Session } from '@opencode-ai/sdk/v2';
 
 import { ChatInput } from './ChatInput';
 import { useUIStore } from '@/stores/useUIStore';
-import { toast } from '@/components/ui';
-import { formatSessionAsMarkdown, downloadAsMarkdown, buildExportFilename } from '@/lib/exportSession';
 import { Skeleton } from '@/components/ui/skeleton';
 import ChatEmptyState from './ChatEmptyState';
 import MessageList, { type MessageListHandle } from './MessageList';
@@ -411,23 +409,6 @@ export const ChatContainer: React.FC = () => {
     const isDesktopExpandedInput = isExpandedInput && !isMobile;
     const messageListRef = React.useRef<MessageListHandle | null>(null);
 
-    const currentSession = React.useMemo(
-        () => currentSessionId ? sessions.find((s) => s.id === currentSessionId) ?? null : null,
-        [currentSessionId, sessions],
-    );
-
-    const handleExportMarkdown = React.useCallback(() => {
-        if (!currentSessionId || sessionMessages.length === 0) {
-            toast.error('Nothing to export');
-            return;
-        }
-        const title = currentSession?.title ?? null;
-        const markdown = formatSessionAsMarkdown(sessionMessages, title);
-        const filename = buildExportFilename(title);
-        downloadAsMarkdown(markdown, filename);
-        toast.success('Session exported');
-    }, [currentSessionId, currentSession, sessionMessages]);
-
     const parentSession = React.useMemo(() => {
         if (!currentSessionId) return null;
         const current = sessions.find((session) => session.id === currentSessionId);
@@ -459,20 +440,6 @@ export const ChatContainer: React.FC = () => {
         </Button>
     ) : null;
 
-    const exportButton = !isMobile && sessionMessages.length > 0 ? (
-        <Button
-            type="button"
-            variant="ghost"
-            size="xs"
-            onClick={handleExportMarkdown}
-            className="absolute right-3 top-3 z-20 !font-normal text-muted-foreground hover:text-foreground"
-            aria-label="Export session as Markdown"
-            title="Export session as Markdown"
-        >
-            <RiDownloadLine className="h-4 w-4" />
-        </Button>
-    ) : null;
-
     React.useEffect(() => {
         if (!currentSessionId && !draftOpen) {
             openNewSessionDraft();
@@ -814,7 +781,6 @@ export const ChatContainer: React.FC = () => {
             style={isMobile ? { paddingBottom: 'var(--oc-keyboard-inset, 0px)' } : undefined}
         >
             {returnToParentButton}
-            {exportButton}
             <ChatViewport
                 currentSessionId={currentSessionId}
                 isDesktopExpandedInput={isDesktopExpandedInput}