Banner (responsive tiers: full logo -> compact rule -> text -> hidden),
SessionPanel (fixed hero track + flexible info track, the desktop pane
shell's fixed-vs-flex contract), floating overlays, prompt zone, and the
pickers all render through WidgetGrid instead of hand-rolled flex math.
Pickers gain maxWidth so grid cells can cap them.
Rebase of the widget-grid PR onto current main, then grow it into a real
2-axis engine: resolveGridTracks (grid-template tracks — fixed cell counts
and weighted fr shares with mins), layoutWidgetGrid (1D auto-packing flow),
and layoutGridAreas (2D absolute placement with row/col spans and implicit
row growth). Overlay/Dialog primitives give zoned viewport-level modals
with an optional scrim. /grid-test (interactive: areas, nesting, zoom,
gap/padding) and /grid-test streams (4x3 mission-control GridAreas board
with promote-to-main) exercise everything end to end.
