fix(live-preview): don't steal editor focus on iframe click in design mode

In design mode the editor area is collapsed, so pulling focus into it
when the user clicks/Escapes inside the live preview or markdown viewer
iframe is disorienting. Gate all such focus-shift paths on
WorkspaceManager.isInDesignMode():

- _focusEditorIfNeeded and the no-liveDoc fallback in LiveDevProtocol
  (HTML live preview edit/highlight click flow)
- focusActiveEditorIfFocusInLivePreview helper (md viewer preview-mode
  click, md viewer Escape, HTML iframe Escape)

Cursor positioning is preserved so the cursor still lands correctly if
the user later switches out of design mode.

Author: abose

src/LiveDevelopment/MultiBrowserImpl/protocol/LiveDevProtocol.js

@@ -53,7 +53,8 @@ define(function (require, exports, module) {
         HTMLInstrumentation   = require("LiveDevelopment/MultiBrowserImpl/language/HTMLInstrumentation"),
         StringUtils = require("utils/StringUtils"),
         FileViewController    = require("project/FileViewController"),
-        MainViewManager     = require("view/MainViewManager");
+        MainViewManager     = require("view/MainViewManager"),
+        WorkspaceManager    = require("view/WorkspaceManager");
 
     const LIVE_DEV_REMOTE_SCRIPTS_FILE_NAME = `phoenix_live_preview_scripts_instrumented_${StringUtils.randomString(8)}.js`;
     const LIVE_DEV_REMOTE_WORKER_SCRIPTS_FILE_NAME = `pageLoaderWorker_${StringUtils.randomString(8)}.js`;
@@ -189,6 +190,9 @@ define(function (require, exports, module) {
      * @private
      */
     function _focusEditorIfNeeded(editor, tagName, contentEditable) {
+        if (WorkspaceManager.isInDesignMode()) {
+            return;
+        }
         const focusShouldBeInLivePreview = ['INPUT', 'TEXTAREA'].includes(tagName) || contentEditable;
         if(focusShouldBeInLivePreview){
             return;
@@ -247,7 +251,9 @@ define(function (require, exports, module) {
             activeEditorPath = activeEditor ? activeEditor.document.file.fullPath : null,
             activeFullEditorPath = activeFullEditor ? activeFullEditor.document.file.fullPath : null;
         if(!liveDocPath){
-            activeEditor && activeEditor.focus(); // restore focus from live preview
+            if (activeEditor && !WorkspaceManager.isInDesignMode()) {
+                activeEditor.focus(); // restore focus from live preview
+            }
             return;
         }
         const allOpenFileCount = MainViewManager.getWorkingSetSize(MainViewManager.ALL_PANES);

src/extensionsIntegrated/Phoenix-live-preview/utils.js

@@ -39,12 +39,16 @@ define(function (require, exports, module) {
     const LIVE_PREVIEW_IFRAME_ID = "panel-live-preview-frame";
     const MDVIEWR_IFRAME_ID = "panel-md-preview-frame";
     const EditorManager      = require("editor/EditorManager");
+    const WorkspaceManager   = require("view/WorkspaceManager");
     // File-type classification helpers live in a shared utility module so
     // non-live-preview code (e.g. Quick Open in design mode) can use them
     // without depending on this extension.
     const FileTypeUtils      = require("utils/FileTypeUtils");
 
     function focusActiveEditorIfFocusInLivePreview() {
+        if (WorkspaceManager.isInDesignMode()) {
+            return;
+        }
         const editor  = EditorManager.getActiveEditor();
         if(!editor){
             return;