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/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 {