The B8 comparison overlay shipped behind a Settings → Dashboard Select
buried 3 clicks deep. The brief asked for "mobile-friendly comparison
toggle (not a fragile hover-only interaction)" and the toggle that
shipped failed that bar — flipping Vormonat / Vorjahr meant a 5-step
round-trip every time.
New `<CompareToggle>` segmented control (None / Vormonat / Vorjahr)
sits next to the dashboard greeting and on the insights page hero.
Persists via the same `/api/dashboard/widgets` PUT the Settings
section already uses, with optimistic update + cache invalidation so
the chart overlays + tile callouts respond instantly. 44 px (min-h-11)
tap targets, focus-visible ring, role=group + aria-label for screen
readers, EN+DE i18n.
6 SSR tests pin segment count, persisted-active state, tap-target
floor, EN+DE labels, and ARIA shape.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
