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.

scripts/extract-traces.test.ts

@@ -175,8 +175,8 @@ describe("live requirements.md", () => {
 
     expect(defined.UR).toBe(75);
     expect(defined.IR).toBe(32);
-    expect(defined.DR).toBe(159);
+    expect(defined.DR).toBe(164);
     expect(defined.JA).toBe(35);
-    expect(defined.total).toBe(301);
+    expect(defined.total).toBe(306);
   });
 });