Merge branch 'master' into worktree-mosaic-library

Renumbers the mosaic's requirement IDs out of the way of the download work
that landed on master in parallel: it had already claimed DR-163/DR-164 and
UT-162, so the mosaic layout is now DR-172, the library favourites scope
DR-173, and its composition test UT-167.

Note for the download branch: its UT-162..UT-165 rows trace to DR-163..DR-166,
none of which are defined in requirements.md — that branch defined DR-167..171
instead. Those references are orphaned and want a look; nothing here touches
them.

src/lib/api/bindings.ts

@@ -870,13 +870,32 @@ async getDownloads(userId: string, statusFilter: string[] | null) : Promise<Down
     return await TAURI_INVOKE("get_downloads", { userId, statusFilter });
 },
 /**
- * Pause a download
+ * Pause a download.
+ * 
+ * Writing `status = 'paused'` is only half of it, and used to be all of it: the
+ * streaming task knew nothing about the row and kept running, then overwrote it
+ * with `completed`/`failed` when it finished. The row flicked to "paused" and
+ * undid itself — the reported "pause does not work". Signalling the worker is
+ * what actually stops the bytes; it leaves the `.part` file in place so
+ * [`resume_download`] can continue from it.
+ * 
+ * A queued (not yet started) download has no worker to signal, and the status
+ * write alone is enough — the pump skips anything that is not `pending`.
+ * 
+ * TRACES: UR-055 | DR-168
  */
 async pauseDownload(downloadId: number) : Promise<null> {
     return await TAURI_INVOKE("pause_download", { downloadId });
 },
 /**
- * Resume a paused download
+ * Resume a paused download.
+ * 
+ * Flipping the row back to `pending` is likewise not enough on its own: the
+ * pump is not a poller, it runs when something calls it, so a resumed download
+ * sat untouched until some unrelated event happened to pump the queue. That is
+ * the other half of "resume does not work".
+ * 
+ * TRACES: UR-055 | DR-168
  */
 async resumeDownload(downloadId: number) : Promise<null> {
     return await TAURI_INVOKE("resume_download", { downloadId });
@@ -2063,7 +2082,7 @@ export type Library = { id: string; name: string; collectionType: string; imageT
  * collection-type → category table any more than an item-type one. See
  * `SearchScope::for_collection_type`.
  * 
- * TRACES: UR-075 | DR-164
+ * TRACES: UR-075 | DR-173
  */
 favoritesScope?: SearchScope | null }
 /**

src/lib/components/common/CachedImage.svelte

@@ -15,7 +15,7 @@
      * Called once the bitmap is decoded, with its intrinsic pixel size. Lets a
      * layout that sizes boxes from artwork (the mosaic) use the shape the image
      * actually has rather than the one its item type suggests.
-     * TRACES: UR-075 | DR-163
+     * TRACES: UR-075 | DR-172
      */
     onNaturalSize?: (width: number, height: number) => void;
   }

src/lib/components/library/MosaicGrid.svelte

@@ -11,7 +11,7 @@
   arrives over a few hundred milliseconds, and re-packing on each arrival would
   shuffle the grid under the viewer's cursor several times over.
 
-  TRACES: UR-075 | DR-163
+  TRACES: UR-075 | DR-172
 -->
 <script lang="ts" generics="T extends { key: string; ratio: number }">
   import type { Snippet } from "svelte";

src/lib/components/library/MosaicTile.svelte

@@ -7,7 +7,7 @@
   lines would no longer line up with its neighbours. Keeping everything inside
   the box is what lets `layoutMosaic` own the geometry completely.
 
-  TRACES: UR-075 | DR-163
+  TRACES: UR-075 | DR-172
 -->
 <script lang="ts">
   import type { Snippet } from "svelte";

src/lib/components/library/libraryMosaic.ts

@@ -9,7 +9,7 @@
 // `favoritesScope` (Rust: `SearchScope::for_collection_type`). This file only
 // decides what to *call* it and where to put it.
 //
-// TRACES: UR-075, UR-067 | DR-163, DR-164 | UT-162
+// TRACES: UR-075, UR-067 | DR-172, DR-173 | UT-167
 
 import type { Library } from "$lib/api/types";
 import {

src/lib/components/library/mosaic.ts

@@ -9,7 +9,7 @@
 //
 // Presentation only — nothing here knows what a library or a media item is.
 //
-// TRACES: UR-075 | DR-163 | UT-158, UT-159, UT-160
+// TRACES: UR-075 | DR-172 | UT-158, UT-159, UT-160
 
 /** A tile to place: an opaque key and the aspect ratio (width / height) to honour. */
 export interface MosaicInput {

src/lib/utils/favoritesView.ts

@@ -41,7 +41,7 @@ export function resolveFavoritesScope(raw: string | null | undefined): Favorites
  * than folded into "all": a caller asking "which category is this?" wants no
  * answer, not the cross-category one.
  *
- * TRACES: UR-075 | DR-164
+ * TRACES: UR-075 | DR-173
  */
 export function asFavoritesScope(
   scope: SearchScope | null | undefined,

src/routes/+page.svelte

@@ -118,7 +118,7 @@
   // The shortcut strip is a mosaic row: one height, each tile as wide as its own
   // artwork. It used to force 16:9 on everything so square music covers lined up
   // with wide backdrops — which lined them up by cropping the covers.
-  // TRACES: UR-075 | DR-163
+  // TRACES: UR-075 | DR-172
   const LIBRARY_STRIP_HEIGHT = 132;
   const libraryTiles = $derived(
     shortcutLibraries.map((lib) => ({ key: lib.id, ratio: assumedLibraryRatio(lib), library: lib }))

src/routes/library/+page.svelte

@@ -45,7 +45,7 @@
   // The overview is a mosaic: rows of one height, tiles of their own widths, so
   // a square music cover sits beside a wide backdrop without either being
   // cropped to the other's shape. Each category also gets a favourites tile of
-  // its own, beside the library it belongs to. TRACES: UR-075 | DR-163, DR-164
+  // its own, beside the library it belongs to. TRACES: UR-075 | DR-172, DR-173
   const mosaicEntries = $derived(buildLibraryMosaic(visibleLibraries));
 
   // Track if we've done an initial load and previous server state
@@ -255,7 +255,7 @@
              category's own favourites sits beside its library — a labelled tile
              at the same weight as a library is the difference between a feature
              people find and one they don't. ux-flows §5C.2.
-             TRACES: UR-067, UR-075 | DR-117, DR-163 -->
+             TRACES: UR-067, UR-075 | DR-117, DR-172 -->
         <MosaicGrid items={mosaicEntries} gap={8}>
           {#snippet tile(entry)}
             {#if entry.kind === "favorites"}