Convert all 41 TypeScript source/config files in cc4e-course/quiz-project
(Next.js), gstack (Astro), and superpowers (Vite/React/Phaser) to plain
JavaScript with JSDoc type annotations, replacing tsconfig.json with
jsconfig.json (strict + checkJs) in each subproject. No behavior changes:
lint, typecheck, test, and build gates match their TypeScript baselines
exactly in all three subprojects. Update stack references in the affected
READMEs accordingly.
