fix: fix value editor scrolling and add selection highlight

- Fix value editor not scrollable when content exceeds container
  (overflow-hidden -> overflow-auto)
- Extract vscodeSelectionLayer from QueryEditor into shared module
  and apply to value editor for consistent selection highlighting

apps/desktop/src/components/grid/DataGrid.vue

@@ -5299,7 +5299,7 @@ defineExpose({
                       v-else
                       ref="valueEditorContainer"
                       data-cell-detail-editor-root
-                      class="min-h-0 flex-1 w-full rounded border overflow-hidden"
+                      class="min-h-0 flex-1 w-full rounded border overflow-auto"
                     />
                   </div>
                   <div class="flex gap-1 mt-2 shrink-0">