Bundle the pure core API for Node consumers

[PBandDev]

Summary

• bundle the comfyui-node-organizer/core export with Vite and keep declaration output in lib/
• revert shared pure-core source imports back to extensionless TypeScript imports and add packaging regression tests
• tighten the README library section so end users can ignore it and developers know when the subpath matters

Test Plan

• pnpm build
• pnpm test:lib
• pnpm typecheck
• pnpm test
• pnpm setup:e2e
• pnpm test:e2e