ci: add release workflow for crates.io and npm distribution

[developer0hye]

Summary

• Add cross-platform release CI triggered by v* tag push
• Publish Rust crates to crates.io (marknest-core → marknest → marknest-server)
• Distribute CLI binary via npm platform-specific packages (npx marknest)
• Build matrix: macOS arm64/x64, Linux x64/arm64, Windows x64
• Create GitHub Releases with binary assets

Key changes

• Cargo.toml: Publish metadata (description, repository, keywords, categories) for all crates
• LICENSE: MIT license file
• npm/: Umbrella package with JS shim + 5 platform-specific binary packages
• .github/workflows/release.yml: Full release pipeline (build → crates.io → npm → GitHub Release)
• scripts/version-bump.sh: Syncs version across all Cargo.toml and npm package.json files
• README.md: Installation section (cargo, npm/npx, from source)

How to release

./scripts/version-bump.sh 0.1.0
git commit -am 'chore: bump version to 0.1.0'
git tag v0.1.0
git push && git push --tags

Required GitHub secrets

• CARGO_REGISTRY_TOKEN: crates.io API token
• NPM_TOKEN: npm automation access token

Test plan

• cargo check passes with updated Cargo.toml
• All 114 tests pass
• cargo publish --dry-run succeeds for marknest-core
• Verify release workflow after merging (push a tag)
• Verify crate names available on crates.io
• Verify marknest name available on npm

🤖 Generated with Claude Code