Allow notebook cell editor taking focus when it's on body. The notebook can...

Allow notebook cell editor taking focus when it's on body. The notebook can lose focus, eg when scrolling a focused cell element out of view, then it goes to body.
Fix #129432

src/vs/workbench/contrib/notebook/browser/view/renderers/codeCell.ts

@@ -60,7 +60,11 @@ export class CodeCell extends Disposable {
 				templateData.editor.setModel(model);
 				viewCell.attachTextEditor(templateData.editor);
 				const focusEditorIfNeeded = () => {
-					if (notebookEditor.getActiveCell() === viewCell && viewCell.focusMode === CellFocusMode.Editor && this.notebookEditor.hasEditorFocus()) {
+					if (
+						notebookEditor.getActiveCell() === viewCell &&
+						viewCell.focusMode === CellFocusMode.Editor &&
+						(this.notebookEditor.hasEditorFocus() || document.activeElement === document.body)) // Don't steal focus from other workbench parts, but if body has focus, we can take it
+					{
 						templateData.editor?.focus();
 					}
 				};

src/vs/workbench/contrib/notebook/browser/view/renderers/markdownCell.ts

@@ -296,7 +296,9 @@ export class StatefulMarkdownCell extends Disposable {
 	}
 
 	private focusEditorIfNeeded() {
-		if (this.viewCell.focusMode === CellFocusMode.Editor && this.notebookEditor.hasEditorFocus()) {
+		if (
+			this.viewCell.focusMode === CellFocusMode.Editor &&
+			(this.notebookEditor.hasEditorFocus() || document.activeElement === document.body)) { // Don't steal focus from other workbench parts, but if body has focus, we can take it
 			this.editor?.focus();
 		}
 	}