fix(ui): show panel toggle button in all modes (not just non-compact)

desktop/src/components/ChatArea.tsx

@@ -361,13 +361,11 @@ export function ChatArea({ compact, onOpenDetail }: { compact?: boolean; onOpenD
               <Search className="w-3.5 h-3.5" />
             </Button>
           )}
-          {/* Side panel toggle — Trae Solo style, in header */}
-          {!compact && (
-            <PanelToggleButton
-              panelOpen={artifactPanelOpen}
-              onToggle={() => setArtifactPanelOpen(!artifactPanelOpen)}
-            />
-          )}
+          {/* Side panel toggle — Trae Solo style, always in header */}
+          <PanelToggleButton
+            panelOpen={artifactPanelOpen}
+            onToggle={() => setArtifactPanelOpen(!artifactPanelOpen)}
+          />
           {/* 详情按钮 (简洁模式) */}
           {compact && onOpenDetail && (
             <Button