feat(downloads): browsable downloaded library with on-disk usage

Replace the flat download list with a Downloaded browse surface that
reuses the online grids/cards/detail pages, filtered to on-device media,
plus a demoted Transfers tab. Add repository browse commands
(getDownloadedLibraries/Items, disk usage) with offline/hybrid
implementations, a downloadedCatalog service, formatBytes helper, and
per-item/device disk-usage labels on cards and grids. Regenerated
bindings.

Also carries the inseparable UR-052 offline-filter hunks in
offline.rs/hybrid.rs.

TRACES: UR-055 | DR-081, DR-082, DR-083, DR-084; UR-056 | DR-085

src/lib/components/library/LibraryGrid.svelte

@@ -1,3 +1,4 @@
+<!-- TRACES: UR-029, UR-051 | DR-069, DR-070 -->
 <script lang="ts">
   import type { MediaItem, Library } from "$lib/api/types";
   import MediaCard from "./MediaCard.svelte";
@@ -9,12 +10,20 @@
     title?: string;
     loading?: boolean;
     showViewToggle?: boolean;
-    forceGrid?: boolean;
     musicContent?: boolean;
     onItemClick?: (item: MediaItem | Library) => void;
+    /**
+     * Optional per-item secondary label (e.g. on-disk size for the Downloaded
+     * surface), forwarded to each card. TRACES: UR-056 | DR-085
+     */
+    sizeLabelFor?: (item: MediaItem | Library) => string | undefined;
+    /** Optional per-item container download badge for the Downloaded surface. */
+    downloadedBadgeFor?: (item: MediaItem | Library) => "full" | "partial" | undefined;
+    /** Optional per-item remove-from-device handler for the Downloaded surface. */
+    onItemRemove?: (item: MediaItem | Library) => void;
   }
 
-  let { items, title, loading = false, showViewToggle = true, forceGrid = false, musicContent = false, onItemClick }: Props = $props();
+  let { items, title, loading = false, showViewToggle = true, musicContent = false, onItemClick, sizeLabelFor, downloadedBadgeFor, onItemRemove }: Props = $props();
 </script>
 
 <div class="space-y-4">
@@ -65,7 +74,7 @@
     <div class="text-center py-12 text-gray-400">
       <p>No items found</p>
     </div>
-  {:else if !forceGrid && $viewMode === "list"}
+  {:else if $viewMode === "list"}
     <LibraryListView {items} showProgress={true} onItemClick={onItemClick} />
   {:else}
     <div class="grid grid-cols-2 sm:grid-cols-3 md:grid-cols-4 lg:grid-cols-5 xl:grid-cols-6 gap-4">
@@ -74,6 +83,9 @@
           <MediaCard
             {item}
             showProgress={true}
+            sizeLabel={sizeLabelFor?.(item)}
+            downloadedBadge={downloadedBadgeFor?.(item)}
+            onRemove={onItemRemove ? () => onItemRemove(item) : undefined}
             onclick={() => onItemClick?.(item)}
           />
         </div>