[web] Add a focus mode to the editor (#32245)

* Basic focus mode implementation

* Exit button

* Toggle between editor pdf mode

* Keep the rail and file tree mounted for editor tabs to work properly

* Hide Switch to editor button in focus mode

* Show shortcuts in layout menu

* Gate the feature behind a focus-mode feature flag

* Add split test badges in the focus mode dropdown item and top bar

* Add analytics tracking for focusMode changes

* Cleanup leftover IdeView value

* Allow passing focusMode value in layout test provider

* Remove redundant listener for focus mode shortcut

* Update focus mode and full project search listeners to use the event key

* Post-rebase cleanup

---------

Co-authored-by: Anna Fields <acfields11@gmail.com>
GitOrigin-RevId: 207f8d136fa6662558c474cca4a867a9842191e7

services/web/frontend/js/features/pdf-preview/components/pdf-preview-hybrid-toolbar.tsx

@@ -1,3 +1,4 @@
+import { useLayoutContext } from '@/shared/context/layout-context'
 import { memo } from 'react'
 import { useTranslation } from 'react-i18next'
 import OLButtonToolbar from '@/shared/components/ol/ol-button-toolbar'
@@ -34,6 +35,7 @@ function PdfPreviewHybridToolbar() {
 }
 
 function PdfPreviewHybridToolbarInner() {
+  const { focusMode } = useLayoutContext()
   return (
     <>
       <div className="toolbar-pdf-left">
@@ -43,7 +45,7 @@ function PdfPreviewHybridToolbarInner() {
       </div>
       <div className="toolbar-pdf-right">
         <div className="toolbar-pdf-controls" id="toolbar-pdf-controls" />
-        <SwitchToEditorButton />
+        {!focusMode && <SwitchToEditorButton />}
         <DetachedSynctexControl />
         {/* TODO: should we have code check? */}
       </div>