Redesign to iOS-grade minimal

Replace the editorial look — serif display type, warm paper tones,
particle canvas, scroll-scrubbed diagrams — with a restrained system:
cool neutrals, hairline rules, a single indigo accent, one sans family
at real weights, tabular numerals everywhere.

The hero is now the product: a static pixel-accurate render of the
dashboard with representative data, in place of abstract animation.
Feature narrative becomes a bento grid of small true artifacts — the
score's weighted terms, an interactive mode switcher over a single
return/privacy weight bar, split and timing visualisations, the
assertNeverUnshields contract, and the closed loop.

Landing drops from nine sections to seven and loses ~500 lines of
decorative component code. Dashboard and shield flow restyled to the
same language: grouped lists, tinted state chips, segmented controls,
glass header.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>