fix(board): show total count in Done column and infinite scroll (#498)

* fix(board): show total count in Done column header and auto-load on scroll

- Column header now shows server-side doneTotal instead of loaded count
- Replace "Load more" button with IntersectionObserver sentinel for
  infinite scroll in the Done column

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(board): move sentinel below imports and stabilize observer

- Move InfiniteScrollSentinel after all import statements
- Use callback ref to avoid recreating IntersectionObserver on every render

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/features/issues/components/board-column.tsx

@@ -23,11 +23,13 @@ export function BoardColumn({
   status,
   issueIds,
   issueMap,
+  totalCount,
   footer,
 }: {
   status: IssueStatus;
   issueIds: string[];
   issueMap: Map<string, Issue>;
+  totalCount?: number;
   footer?: ReactNode;
 }) {
   const cfg = STATUS_CONFIG[status];
@@ -54,7 +56,7 @@ export function BoardColumn({
             {cfg.label}
           </span>
           <span className="text-xs text-muted-foreground">
-            {issueIds.length}
+            {totalCount ?? issueIds.length}
           </span>
         </div>
 

apps/web/features/issues/components/board-view.tsx

@@ -33,6 +33,30 @@ import { StatusIcon } from "./status-icon";
 import { BoardColumn } from "./board-column";
 import { BoardCardContent } from "./board-card";
 
+/** Sentinel that triggers `onVisible` when scrolled into view. */
+function InfiniteScrollSentinel({ onVisible, loading }: { onVisible: () => void; loading: boolean }) {
+  const sentinelRef = useRef<HTMLDivElement>(null);
+  const onVisibleRef = useRef(onVisible);
+  onVisibleRef.current = onVisible;
+
+  useEffect(() => {
+    const node = sentinelRef.current;
+    if (!node) return;
+    const observer = new IntersectionObserver(
+      ([entry]) => { if (entry.isIntersecting) onVisibleRef.current(); },
+      { rootMargin: "100px" },
+    );
+    observer.observe(node);
+    return () => observer.disconnect();
+  }, []);
+
+  return (
+    <div ref={sentinelRef} className="flex items-center justify-center py-2">
+      {loading && <Loader2 className="size-3 animate-spin text-muted-foreground" />}
+    </div>
+  );
+}
+
 const COLUMN_IDS = new Set<string>(ALL_STATUSES);
 
 const kanbanCollision: CollisionDetection = (args) => {
@@ -111,7 +135,7 @@ export function BoardView({
 }) {
   const sortBy = useViewStore((s) => s.sortBy);
   const sortDirection = useViewStore((s) => s.sortDirection);
-  const { loadMore, hasMore, isLoading: loadingMore } = useLoadMoreDoneIssues();
+  const { loadMore, hasMore, isLoading: loadingMore, doneTotal } = useLoadMoreDoneIssues();
 
   // --- Drag state ---
   const [activeIssue, setActiveIssue] = useState<Issue | null>(null);
@@ -274,19 +298,10 @@ export function BoardView({
             status={status}
             issueIds={columns[status] ?? []}
             issueMap={issueMapRef.current}
+            totalCount={status === "done" ? doneTotal : undefined}
             footer={
               status === "done" && hasMore ? (
-                <button
-                  type="button"
-                  className="mt-1 flex w-full items-center justify-center gap-1.5 rounded-md py-2 text-xs text-muted-foreground hover:bg-accent/60 transition-colors disabled:opacity-50"
-                  onClick={loadMore}
-                  disabled={loadingMore}
-                >
-                  {loadingMore ? (
-                    <Loader2 className="size-3 animate-spin" />
-                  ) : null}
-                  {loadingMore ? "Loading..." : "Load more"}
-                </button>
+                <InfiniteScrollSentinel onVisible={loadMore} loading={loadingMore} />
               ) : undefined
             }
           />