feat(timeline): focus follows archive, snaps to first on view load

- New selection.focusAfter(excluded) walks selection.order forward past
  the archived/restored set so X-ing through the timeline keeps the
  cursor on the next live photo instead of falling back to photo[0]
  via the auto-anchor effect. Wired into gridKeyNav.toggleArchive (X
  key) and BulkActionBar.onArchive.
- Auto-focus effect on the timeline always re-anchors to photos[0] on
  view load (pageCount → 1), instead of preserving a stale uid from
  the previous filter.
- PhotoGrid re-anchors focus when the previously focused uid isn't in
  the new photo set, so drilling into a /tags category drops the
  cursor on its first tile instead of carrying a stale selection from
  whatever view the user came from.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/src/lib/actions/gridKeyNav.ts

@@ -17,6 +17,7 @@ import { filters } from '$lib/stores/filters.svelte';
 import { closePreview, openPreview, preview } from '$lib/stores/preview.svelte';
 import {
 	clearSelection,
+	focusAfter,
 	indexOf,
 	selectRange,
 	selection,
@@ -218,6 +219,12 @@ export function gridKeyNav(node: HTMLElement, params: GridKeyNavParams = {}) {
 			toast.error(err instanceof Error ? err.message : 'Archive failed');
 			return;
 		}
+		// Move focus forward before the photos query refetches, so the
+		// user can keep X-ing through the timeline without their cursor
+		// snapping back to photo[0]. Walks past every uid we just
+		// archived/restored — relevant when the cull targets came from a
+		// multi-selection rather than the single focused tile.
+		focusAfter(ids);
 		invalidatePhotos(ids);
 		const label = target ? `Archived ${ids.length}` : `Restored ${ids.length}`;
 		toast.success(label);
@@ -344,12 +351,27 @@ export function gridKeyNav(node: HTMLElement, params: GridKeyNavParams = {}) {
 			return;
 		}
 		try {
-			await addToHeap(heap.UID, ids);
+			const { added } = await addToHeap(heap.UID, ids);
 			void queryClient.invalidateQueries({ queryKey: ['heaps'] });
 			void queryClient.invalidateQueries({ queryKey: ['photos'] });
-			toast.success(`Added ${ids.length} → ${heap.Title}`);
-			pushUndo(`Added ${ids.length} to ${heap.Title}`, async () => {
-				await removeFromHeap(heap.UID, ids);
+			// PhotoPrism returns 200 even when nothing was added — distinguish
+			// "really added N" from "skipped all N" so the toast tells the
+			// truth.
+			if (added.length === 0) {
+				toast.error(`Nothing added to ${heap.Title}`, {
+					description: `PhotoPrism rejected all ${ids.length} UIDs (already in heap, or not indexed).`
+				});
+				return;
+			}
+			if (added.length < ids.length) {
+				toast.success(`Added ${added.length}/${ids.length} → ${heap.Title}`, {
+					description: 'The rest were already in this heap.'
+				});
+			} else {
+				toast.success(`Added ${added.length} → ${heap.Title}`);
+			}
+			pushUndo(`Added ${added.length} to ${heap.Title}`, async () => {
+				await removeFromHeap(heap.UID, added);
 				void queryClient.invalidateQueries({ queryKey: ['heaps'] });
 				void queryClient.invalidateQueries({ queryKey: ['photos'] });
 			});