feat: publish core API to npm

[PBandDev]

Summary

• Remap exports so "." points at lib/core.js (drop ./core subpath)
• Add main/module/types fallback fields for older tooling
• Move typescript/vite to devDependencies (zero runtime deps)
• Add files field to limit tarball to lib/ + README.md
• Add parallel publish-npm job in publish workflow using NPM_TOKEN secret
• Update smoke test, README, and AGENTS.md to reflect bare import path

Test plan

• pnpm typecheck passes
• pnpm test — 197 tests pass
• pnpm test:lib — smoke test passes with bare comfyui-node-organizer import
• Verify NPM_TOKEN secret is set (confirmed via gh secret list)
• First real publish on next release dispatch