fix(fe): KsDataGrid - remove onCellFocused to allow Enter key navigation

Problem: onCellFocused was auto-starting edit mode on every focus,
preventing AG Grid's native Enter-key navigation from working.

Solution: Remove onCellFocused function and @cell-focused event handler.

Now Enter key can properly navigate to next cell (Tab behavior).

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

frontend/src/shared/ui/components/KsDataGrid.vue

@@ -20,8 +20,7 @@ import {
   type ColDef,
   type RowClickedEvent,
   type CellValueChangedEvent,
-  type RowClassParams,
-  type CellFocusedEvent
+  type RowClassParams
 } from 'ag-grid-community'
 import type { UiGridColumn } from '../adapter/contracts'
 
@@ -113,26 +112,6 @@ function onCellValueChanged(event: CellValueChangedEvent): void {
   }
 }
 
-function onCellFocused(event: CellFocusedEvent): void {
-  if (event.column && event.rowIndex !== undefined) {
-    const colDef = event.column.getColDef()
-    if (colDef.editable) {
-      const currentEditingCell = event.api.getEditingCell()
-      const focusedColId = event.column.getColId()
-
-      const isSameCell = currentEditingCell &&
-        currentEditingCell.rowIndex === event.rowIndex &&
-        currentEditingCell.column?.getColId() === focusedColId
-
-      if (!isSameCell) {
-        event.api.startEditingCell({
-          rowIndex: event.rowIndex,
-          colKey: focusedColId
-        })
-      }
-    }
-  }
-}
 
 function onSortChanged(params: { api: { redrawRows: () => void; refreshCells: (options: { force: boolean }) => void } }): void {
   params.api.redrawRows()
@@ -208,7 +187,6 @@ defineExpose({ focusRow, redrawRows, gridApi })
       @sort-changed="onSortChanged"
       @row-clicked="onRowClicked"
       @cell-value-changed="onCellValueChanged"
-      @cell-focused="onCellFocused"
     />
   </div>
 </template>