React-specific code shape in the Grida editor. Hooks cannot be tested or benchmarked and silently break tuned UX under layered composition, so they are barred from the engine and main system — load-bearing logic lives in classes and namespaces, hooks only as thin edge wires. `data-testid` follows component-root discipline: one per significant component, not scattered. Use when authoring React in `editor/grida-canvas-react/`, `editor/components/`, `editor/scaffolds/`, or `editor/app/*`.