The dashboard is now a single-screen app shell:
- app-bar page tabs (Model + placeholder Explainer/Findings/Guides) via
lightweight hash routing (usePage); the wordmark links home
- a 2x2 graph grid that fills the viewport, rows sized to half its height so
the four cells always show; a + Add tile is the 4th cell, a 5th scenario
scrolls (with a reserved scrollbar gutter)
- a left settings sidebar exposing the forwarding composite as grouped levers
(novelty, harm awareness, program strength, plus baseline forwarding and
education budget); the card is a CSS container so the sliders stack to width
- a full-width dock (legend, full-width player, Export / Reach over time /
Data table); the reach chart and data table open as overlays
- the illustrative note moved under the hero
ScenarioToolbar is removed (the + tile and the dock Export replace it).
Deviates from the original ui-spec, which is amended with a pointer.
