fix(twenty-front): guard BlockNote backspace handler against top-level node position

https://sonarly.com/issue/33776?type=bug

Pressing Backspace at the beginning of the first block in a Dashboard rich text widget throws an unhandled RangeError from ProseMirror, crashing the editor.

Fix: Added a tiptap Extension (`backspaceTopLevelGuard`) that intercepts Backspace keypresses at the beginning of the first top-level block in BlockNote editors, preventing BlockNote 0.47.x's internal parent-block traversal from calling `resolvedPos.before(0)` which throws `RangeError: "There is no position before the top-level node"`.

The extension:
1. Only activates on Backspace with an empty (collapsed) selection
2. Checks if the cursor is at offset 0 within a node at depth ≤ 2 (BlockNote's doc → blockGroup → blockContainer structure)
3. Confirms the position is at the document start (`$from.before($from.depth) === 1`)
4. Returns `true` (handled) to swallow the keypress — there is nothing to delete at this position anyway

Applied to both `useCreateBlockNote` call sites:
- `StandaloneRichTextEditorContent.tsx` (Dashboard rich text widget — the crash site from the Sentry event)
- `RichTextFieldEditor.tsx` (Record field rich text editor — same BlockNote version, same potential crash)

Uses `_tiptapOptions.extensions` to inject the guard extension into BlockNote's underlying tiptap editor.

packages/twenty-front/src/modules/blocknote-editor/utils/getBackspaceTopLevelGuardExtension.ts

@@ -0,0 +1,38 @@
+import { Extension } from '@tiptap/core';
+
+// Guards against a BlockNote 0.47.x bug where pressing Backspace at the
+// beginning of the first top-level block throws:
+// RangeError: "There is no position before the top-level node"
+// BlockNote's internal parent-block traversal calls
+// resolvedPos.before(depth - 1) without checking that depth > 1.
+export const getBackspaceTopLevelGuardExtension = () =>
+  Extension.create({
+    name: 'backspaceTopLevelGuard',
+    priority: 1000,
+    addKeyboardShortcuts() {
+      return {
+        Backspace: ({ editor }) => {
+          const { $from, empty } = editor.state.selection;
+
+          if (!empty) {
+            return false;
+          }
+
+          // When the cursor is at the very beginning of the first
+          // top-level block (offset 0 and depth ≤ 2 in BlockNote's
+          // doc → blockGroup → blockContainer structure), swallow the
+          // Backspace to prevent the crash. There is nothing to delete
+          // in this position anyway.
+          if ($from.parentOffset === 0 && $from.depth <= 2) {
+            const atDocStart = $from.before($from.depth) === 1;
+
+            if (atDocStart) {
+              return true;
+            }
+          }
+
+          return false;
+        },
+      };
+    },
+  });

packages/twenty-front/src/modules/object-record/record-field/ui/meta-types/input/components/RichTextFieldEditor.tsx

@@ -5,6 +5,7 @@ import { BLOCK_SCHEMA } from '@/blocknote-editor/blocks/Schema';
 import { BlockEditor } from '@/blocknote-editor/components/BlockEditor';
 import { BLOCK_EDITOR_GLOBAL_HOTKEYS_CONFIG } from '@/blocknote-editor/constants/BlockEditorGlobalHotkeysConfig';
 import { useAttachmentSync } from '@/blocknote-editor/hooks/useAttachmentSync';
+import { getBackspaceTopLevelGuardExtension } from '@/blocknote-editor/utils/getBackspaceTopLevelGuardExtension';
 import { useReplaceBlockEditorContent } from '@/blocknote-editor/hooks/useReplaceBlockEditorContent';
 import { parseInitialBlocknote } from '@/blocknote-editor/utils/parseInitialBlocknote';
 import { prepareBodyWithSignedUrls } from '@/blocknote-editor/utils/prepareBodyWithSignedUrls';
@@ -213,6 +214,9 @@ export const RichTextFieldEditor = ({
     placeholders: {
       default: t`Type '/' for commands, '@' for mentions`,
     },
+    _tiptapOptions: {
+      extensions: [getBackspaceTopLevelGuardExtension()],
+    },
   });
 
   if (editorRef) {

packages/twenty-front/src/modules/page-layout/widgets/standalone-rich-text/components/StandaloneRichTextEditorContent.tsx

@@ -12,6 +12,7 @@ import { filterSupportedBlocks } from '@/page-layout/widgets/standalone-rich-tex
 
 import { BLOCK_EDITOR_GLOBAL_HOTKEYS_CONFIG } from '@/blocknote-editor/constants/BlockEditorGlobalHotkeysConfig';
 import { useAttachmentSync } from '@/blocknote-editor/hooks/useAttachmentSync';
+import { getBackspaceTopLevelGuardExtension } from '@/blocknote-editor/utils/getBackspaceTopLevelGuardExtension';
 import { parseInitialBlocknote } from '@/blocknote-editor/utils/parseInitialBlocknote';
 import { usePushFocusItemToFocusStack } from '@/ui/utilities/focus/hooks/usePushFocusItemToFocusStack';
 import { useRemoveFocusItemFromFocusStackById } from '@/ui/utilities/focus/hooks/useRemoveFocusItemFromFocusStackById';
@@ -79,6 +80,9 @@ export const StandaloneRichTextEditorContent = ({
     placeholders: {
       default: t`Enter text or type '/' for commands`,
     },
+    _tiptapOptions: {
+      extensions: [getBackspaceTopLevelGuardExtension()],
+    },
   });
 
   const handlePersistBody = useDebouncedCallback((blocknote: string) => {