preview: LQIP + ±2 prefetch + bound action bar to its column

Preview pane paints instantly: a blurred copy of the same thumbnail the
grid loaded (cache hit) rides beneath the sharp fit_1280, which now
carries fetchpriority=high and decoding=async. A $effect prefetches
fit_1280 for the ±2 neighbours so arrow-skim hits the HTTP cache.
Carousel thumbs drop to fetchpriority=low so they yield to the main
image. Skeleton grid gains an mt-2 to breathe against the toolbar.
BulkActionBar moves inside the main column in both PreviewModal and the
/tags drill-in so it no longer stretches under the right sidebar.

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

web/src/lib/components/preview/PreviewModal.svelte

@@ -133,7 +133,11 @@
 				Full-screen preview of the focused photo with metadata and a thumbnail carousel.
 			</Dialog.Description>
 
-			<!-- Top row: preview pane (fills) + sidebar (fixed width). -->
+			<!-- Top row: preview pane (fills) + sidebar (fixed width).
+			     BulkActionBar lives inside the main column — same shape as the
+			     timeline (+page.svelte) so the bar stays bounded by the
+			     column's width and doesn't stretch under the metadata
+			     sidebar. -->
 			<div class="flex min-h-0 flex-1">
 				<div class="relative flex min-w-0 flex-1 flex-col">
 					<button
@@ -148,6 +152,8 @@
 					<div class="flex min-h-0 flex-1">
 						<PreviewPane uid={focusedUid} order={selection.order} />
 					</div>
+					<!-- Action toolbar (acts on selection.ids; falls back to focused). -->
+					<BulkActionBar />
 				</div>
 				{#if focusedPhotoQuery.data}
 					<aside
@@ -158,9 +164,6 @@
 				{/if}
 			</div>
 
-			<!-- Action toolbar (acts on selection.ids; falls back to focused). -->
-			<BulkActionBar />
-
 			<!-- Bottom filmstrip across selection.order. -->
 			<PreviewCarousel />
 		</Dialog.Content>