Frontend Structure Rules

Validation rules for future frontend checks:

Page components must not define shared API request/response types.
Route definitions must live under routes/.
API clients must live under api/.
Plugin bridge contracts must live under contracts/.
Validation schemas must live under schemas/.
Visual theme tokens, shared surface styles, and background behavior must live under theme/, and theme/README.md must document the active style contract.
Full-workspace magical ultimate-effect behavior must live in components/MagicalParticleLayer.tsx and be mounted from shared shell chrome, not copied into individual pages.
Shared utilities must live under utils/.