feat(plan): grid renders up to 3 stacked records per cell

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/admin/pages/PlanWork.tsx

@@ -17,7 +17,11 @@ import PlanCategoriesModal from "../components/PlanCategoriesModal";
 import Forbidden from "../components/Forbidden";
 import { Button, Alert, LoadingState, PageEnter } from "../ui";
 import { projectListOptions, type Project } from "../lib/queries/projects";
-import { planCategoriesOptions, type PlanCategory } from "../lib/queries/plan";
+import {
+  planCategoriesOptions,
+  type PlanCategory,
+  type ResolvedCell,
+} from "../lib/queries/plan";
 // plan.css is imported once globally in AdminApp.tsx — no per-page re-import.
 
 const MONTH_NAMES = [
@@ -202,7 +206,8 @@ export default function PlanWork() {
   );
 
   const openCell = useCallback(
-    (userId: number, date: string) => {
+    (userId: number, date: string, _cells: ResolvedCell[]) => {
+      void _cells;
       const cell = getCell(grid, userId, date);
       // Past-date guard: the server rejects create/edit on past dates with
       // a 403 (see assertNotPastDate in plan.service.ts). To keep the user