Sync record selection with the edit mode (#19276)

## PR description

The previous approach used a detached flag to represent selection mode,
which could was not synced sync with actual UI selection state. This
change ties the edit mode's selection/fallback behavior directly to
whether records are truly selected in the record index.

- Removes `commandMenuItemEditSelectionModeState` (a standalone 'none' |
'selection' atom) and replaces it with
`mainContextStoreHasSelectedRecordsSelector`, which derives selection
state from the real record selection in the context store.
- Adds `useSelectFirstRecordForEditMode` to programmatically select the
first record (table row or kanban card) when toggling to selection mode,
and useResetRecordIndexSelection to clear selection when toggling off or
exiting edit mode.
- Ensures record selection is properly cleaned up when exiting layout
customization mode or closing the side panel.

## Video QA

### Table


https://github.com/user-attachments/assets/1d845809-8369-4872-b3a9-a0281b8e464b

### Board


https://github.com/user-attachments/assets/325c2d58-4ca0-408a-ab4a-66b97d9d70de

packages/twenty-front/src/modules/layout-customization/hooks/useEnterLayoutCustomizationMode.ts

@@ -4,7 +4,6 @@ import { useCallback } from 'react';
 import { SidePanelPages } from 'twenty-shared/types';
 import { IconPencil } from 'twenty-ui/display';
 
-import { commandMenuItemEditSelectionModeState } from '@/command-menu-item/server-items/edit/states/commandMenuItemEditSelectionModeState';
 import { commandMenuItemsDraftState } from '@/command-menu-item/server-items/edit/states/commandMenuItemsDraftState';
 import { commandMenuItemsSelector } from '@/command-menu-item/server-items/common/states/commandMenuItemsSelector';
 import { activeCustomizationPageLayoutIdsState } from '@/layout-customization/states/activeCustomizationPageLayoutIdsState';
@@ -51,8 +50,6 @@ export const useEnterLayoutCustomizationMode = () => {
       isSidePanelOpened &&
       currentSidePanelPage === SidePanelPages.CommandMenuDisplay
     ) {
-      store.set(commandMenuItemEditSelectionModeState.atom, 'selection');
-
       navigateSidePanel({
         page: SidePanelPages.CommandMenuEdit,
         pageTitle: t`Edit actions`,