Fix mobile layout key, language picker close handler, and presentation download

- Mobile vertical layout: add key= based on direction so react-resizable-panels
  remounts cleanly when switching between horizontal and vertical; also use
  isVertical (not just pdfLayout) for the autoSaveId to avoid restoring a
  mismatched layout from localStorage
- Language picker: replace stopPropagation pattern with a containment check on
  the document click handler — more robust on React pages where Bootstrap JS or
  React's event delegation can interfere with stopPropagation
- Presentation download dropdown: use popperConfig strategy:'fixed' so the menu
  escapes overflow:hidden table cells; remove forced drop='up' and let Popper
  choose; defer URL.revokeObjectURL by 10 s to give the browser time to start
  the download before the blob URL is released

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/web/frontend/js/features/ide-react/components/layout/main-layout.tsx

@@ -80,8 +80,9 @@ export default function MainLayout() {
           <Panel id="ide-redesign-editor-and-pdf-panel" order={2}>
             <HistoryContainer />
             <PanelGroup
+              key={isVertical ? 'vertical' : 'horizontal'}
               autoSaveId={
-                pdfLayout === 'verticalSplit'
+                isVertical
                   ? 'ide-redesign-editor-and-pdf-panel-group-vertical'
                   : 'ide-redesign-editor-and-pdf-panel-group'
               }