EventTheme
The ambient event branding to apply app-wide — a subtle accent wash, the event palette, and/or the event fonts. Populated at the composition root only when a device is on event firmware and the user hasn't opted out via LocalEventThemeToggle; null everywhere else. AppTheme reads fonts to swap AppTypography; the app bar reads accent for its wash and palette for its brand rule. The event info sheet and branding icon are driven separately by LocalEventBranding so they stay available even when opted out.
Parameters
the edition's primary — calm enough to sit behind title text as a low-alpha wash.
the edition's loud detail color, for small marks that need to pop rather than recede.
every brand color the edition publishes, in authored order; empty when it publishes none.