test(e2e): drive the real hero rotation animation

The unit specs dispatch `animationend` on the dot span by hand, so a fill
whose real event no longer reached the handler would still pass. The new
Electron spec shortens `--hero-rotation-ms` and checks that the running
`::before` fill advances the slide, that pause holds it and that Play
resumes it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/architecture/workspace-dashboard.md

@@ -137,6 +137,9 @@ by id, so a late live slide never moves the user off the current one. Test
 hooks: `dashboard-hero`, `dashboard-hero-slide` (`data-hero-kind`),
 `dashboard-hero-dot`, `dashboard-hero-pause`,
 `dashboard-hero-primary-action`, `dashboard-hero-secondary-action`.
+`dashboard-hero-rotation.e2e.ts` drives the real fill animation (with a
+shortened `--hero-rotation-ms`) to prove its `animationend` still advances
+and that pause holds the slide.
 
 ## Rail Contract