chore(traceability): shift this branch's ids clear of master's

Master allocated DR-224 and UT-211 while this branch was in flight — the third
collision on this work. Everything here moves up by one: DR-224..236 become
DR-225..237, UT-211..213 become UT-212..214. UR-079, UR-080 and IR-033 were
still free and are unchanged.

Mechanical, and matched on each row's own text rather than on its number, so a
row cannot be shifted twice or the wrong one caught. Master's DR-224 (the
background-audio toggle) and UT-211 are untouched.

docs/architecture/02-svelte-frontend.md

@@ -805,7 +805,7 @@ can safely be re-sent on resume.
 ## Stream Transport
 
 **Location**: `src/lib/player/streamTransport.ts`
-**TRACES**: UR-079 | DR-224 | UT-213
+**TRACES**: UR-079 | DR-225 | UT-214
 
 `videoLoaderFor(selection, capabilities)` picks the loader for the webview
 `<video>` element — `hlsjs`, `nativeHls`, or `direct` — from the backend's tagged
@@ -835,7 +835,7 @@ drift apart. The background-audio handoff states the transport it is moving to
 progressive mp3 out, HLS back — via `selectionAt()`, rather than leaving it to be
 inferred.
 
-The quality picker is filled from `selection.available` (DR-226): rungs the
+The quality picker is filled from `selection.available` (DR-227): rungs the
 backend marked `exceedsSource` are not drawn, because they produce the same bytes
 as `Original`. Nothing is optimistically assigned when the viewer picks a rung —
 what the menu shows comes from the selection the backend hands back, since a