Session 37: Design system Phase F — mobile parity: 5-tab bar, More sheet, PWA polish (1872 tests)

VYNDR 2.0 conversion, Phase F (mobile is the PWA we launch first). Frontend-only;
zero backend changes.

- BottomTabBar rewritten to the §6 5-tab spec: Slate/Terminal/Scan/Ledger/More,
  with Scan as the prominent raised grade-green action. Shown for anon too (only
  mobile nav). Integrated More bottom sheet (sheet-up, backdrop dismiss, 48px mono
  rows). iOS safe-area + 44px touch targets.
- Nav hamburger retired on mobile (tab bar owns nav).
- globals.css mobile section: tab-bar hidden >=768, main bottom padding,
  grade-hero 80px, terminal-grid stacks, game-lines horizontal scroll.
- PWA: manifest shortcuts (Slate/Scan/Terminal) + categories; viewport-fit=cover.

Gotcha: `as const` on the TABS array broke type-check (distinct literal types);
fixed with a shared TabDef interface.

19 new tests. Backend 1853 -> 1872, 145 suites, zero regressions. Web build clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/app/layout.tsx

@@ -89,6 +89,9 @@ export const viewport: Viewport = {
   width: 'device-width',
   initialScale: 1,
   maximumScale: 5,
+  // Session 37 — extend under the iOS notch / home indicator so the
+  // mobile tab bar's env(safe-area-inset-*) padding has room to work.
+  viewportFit: 'cover',
 };
 
 export default async function RootLayout({ children }: { children: React.ReactNode }) {