Fix build failures and package exports

[Copilot]

Build was failing with TypeScript module resolution errors for howler, matter-js, and seedrandom after the ECS rewrite. Additionally, npm run check-exports was failing due to mismatched directory names and missing exports configuration.

Changes

• Added npm install step to ensure dependencies are available before build
• Fixed import formatting in demo and documentation files to comply with prettier rules
• Renamed src/new-ecs/ to src/ecs/ to match package.json exports
• Updated all imports throughout the codebase from new-ecs to ecs
• Removed pooling export from package.json since the directory doesn't exist

The TypeScript compiler now correctly resolves type definitions from @types/howler, @types/matter-js, and @types/seedrandom packages, and all package exports are properly configured and validated.

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[stormmuller]

npm run check-exports still fails

[Copilot]

npm run check-exports still fails

Fixed. The issue was that src/new-ecs directory needed to be renamed to src/ecs to match the package.json exports, and the pooling export needed to be removed since that directory doesn't exist. All package exports now resolve correctly. (09cc74f)