LIGHT — the declared light table · slugs and light windows derive at any tick
one declared light table (sunrise · sunset · drift) — everything else derives: DAY/NIGHT/DUSK/DAWN slugs, golden and blue hour windows · 30 days of bands (nights lengthen — the drift is visible), the selected day at hour grain · the scene ledger derives each slug: click a scene to land its clock · SC 12 is authored NIGHT but its chronicle tick is midday — the ledger flags the contradiction (the Setup demo's slug vs the clock: a real finding, deliberately left in) · Setup cards inherit from here — one source of truth for light continuity