Refactor App.tsx from god component to context-based architecture

Replace prop drilling with React context providers. App.tsx shrinks
from 427 lines to ~80 lines of pure layout. Components consume shared
state directly via 7 context providers instead of threading 50+ props.

Key changes:
- 7 context providers wrapping existing hooks (encounter, bestiary,
  player characters, side panel, theme, bulk import, initiative rolls)
- 2 coordinating hooks extracted from App.tsx (useInitiativeRolls,
  useAutoStatBlock)
- All 9 affected components refactored from prop-based to context-based
- 6 test files updated to use providers or context mocks
- Prop count enforcement script (max 8 per component interface)
- Constitution principle II-A added (context-based state flow)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -31,6 +31,7 @@
 		"oxlint": "oxlint --tsconfig apps/web/tsconfig.json --type-aware",
 		"check:ignores": "node scripts/check-lint-ignores.mjs",
 		"check:classnames": "node scripts/check-cn-classnames.mjs",
-		"check": "pnpm audit --audit-level=high && knip && biome check . && oxlint --tsconfig apps/web/tsconfig.json --type-aware && node scripts/check-lint-ignores.mjs && node scripts/check-cn-classnames.mjs && tsc --build && vitest run && jscpd"
+		"check:props": "node scripts/check-component-props.mjs",
+		"check": "pnpm audit --audit-level=high && knip && biome check . && oxlint --tsconfig apps/web/tsconfig.json --type-aware && node scripts/check-lint-ignores.mjs && node scripts/check-cn-classnames.mjs && node scripts/check-component-props.mjs && tsc --build && vitest run && jscpd"
 	}
 }