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>

knip.json

@@ -5,6 +5,6 @@
 			"entry": ["scripts/*.mjs"]
 		},
 		"packages/*": {},
-		"apps/*": {}
+		"apps/web": {}
 	}
 }