fix(home): restart the hero banner timer on a manual change

The rotation interval was installed once when the banner mounted and never
touched again, so a swipe, arrow or dot tap inherited whatever was left of the
running countdown — swiping 5.5s into a 6s interval moved the banner on half a
second later.

The timer moves into heroRotation.ts as a small restartable object so it can be
unit-tested, and every manual navigation path restarts it from that moment.
Verified red-first: with restart() reverted to leave a running timer alone, the
regression test fails.

Release 0.9.1.

docs/defect-windows.md

@@ -36,6 +36,7 @@ went unexercised until a later feature leaned on them.
 | `download_album` read its track list from the local cache (DR-173) | v0.0.1 | **v0.5.5** | ~8 weeks | pickaxe |
 | Device profile carried no `MaxAudioChannels` (DR-141) | v0.0.1 | **v0.4.6** | ~7 weeks | absence |
 | Streaming ceiling fixed at 20 Mbps with no way to lower it (UR-074) | v0.0.1 | **v0.5.3** (as a feature) | ~7.5 weeks | pickaxe |
+| Hero banner auto-rotation never restarted after a manual swipe (DR-038) | v0.0.1 | **v0.9.1** | ~8.5 weeks | pickaxe |
 
 ### Why they took so long to surface
 

docs/requirements.md

@@ -698,6 +698,7 @@ Internal architecture, components, and application logic.
 | UT-205 | Queued download paths cannot escape the download root — traversal, absolute and `..` forms are refused — while the four real path shapes the app builds, including the absolute one `download_series` produces, come back unchanged; and a completed download cannot register a file outside the root | DR-211 | Done |
 | UT-206 | The offline item-type filter is bound rather than interpolated (a value containing a quote and `OR 1=1` matches nothing instead of disabling the `WHERE`), `build_get_items_endpoint` percent-encodes its values while preserving the commas Jellyfin splits on, and volume normalisation clamps out-of-range input and maps NaN to a finite value | DR-212 | Done |
 | UT-200 | The stream a player could only restart is refused its retry: the handoff transcode answers yes to `player_retry_restarts_stream` while music, video and a downloaded episode answer no, and the Kotlin decision starts permissive, flips on a non-resumable load, and is restored by the next ordinary one | DR-203 | Done |
+| UT-207 | The hero banner's rotation timer restarts from the moment of a manual change: a swipe 5.5s into a 6s interval waits a further 6s instead of firing the leftover 500ms, repeated restarts never stack timers, and `stop()` ends rotation | DR-038 | Done |
 
 ### Integration Tests