chore(ds): bump to design system 0.9.0 + full compliance sweep

[42piratas]

Re-vendors tokens at 0.9.0 (0.7.0 -> 0.9.0 is purely additive) and closes
every gap the bump exposes, so the app is DS-compliant end to end rather
than merely pinned.

• The page ground turns white: 0.9.0 resolves --surface to --warm-0, and
  --surface-alt with it, so a card is now told apart from the canvas by its
  border and shadow alone. That makes the elevation pin mandatory: Tailwind
  owns the --shadow-* namespace, so the DS publishes its rungs as --elev-*
  and index.css pins the four of them. Every primitive already writing
  shadow-sm inherits DS elevation with no component edit.
• The DS semantic names are exposed as utilities. The registry sidebar
  paints bg-surface, which resolved to nothing here — the app only ever
  mapped the shadcn aliases, never the token names behind them.
• Control boundaries move to --border-control (new in 0.9.0). WCAG 1.4.11
  wants 3:1 for the visual information identifying a UI component, which the
  card-edge --border does not reach.
• The radius scale stops guessing. The canon has rungs at 6/8/10px and
  nothing outside that; xs and xl were falling through to Tailwind's own
  defaults (2px/12px), a silent fork. Both are clamped to the nearest rung,
  and sm/md/lg are aliased to --r-2/3/4 instead of being derived by calc().
• The 11 registry primitives are re-adopted at 0.9.0. components.json flips
  rsc to true so the CLI stops stripping "use client" from registry sources
  on write — the stripping is what made three of them read as edited. The
  directive is inert in a Vite build.

The compliance gate drops its two escape hatches: it reads the tokens and
the registry from the design-system checkout now (4242labs/design-system#90),
so DS_SKIP_DIFF is gone and Gate 3 diffs for real. Pin moves to 0.9.0.

Validated in Chrome DevTools MCP at 1440x900 and 390x844, both views and
both grounds: white ground, mint mark on ink, no console output.