docs: add interactive playground

[z81]

Summary

• add a separate Sandpack-powered playground with Module, LazyModule, and HKT examples
• resolve packages from imports after 1 second of idle time while keeping execution behind Run
• harden dependency parsing, console output, keyboard focus, and browser coverage

Verification

• npx nx test docs --skip-nx-cache --runInBand (80 passed)
• npx nx test di --skip-nx-cache --runInBand (67 passed)
• npx tsc -p docs/tsconfig.spec.json --noEmit
• npx nx run docs:check --skip-nx-cache
• npx nx run docs:build --skip-nx-cache
• focused Playwright playground contract

The full docs smoke reaches the playground successfully, then still hits the pre-existing Monaco hover timeout.