Add npm and Claude Code distribution

[Mrbaeksang]

Summary

• add the setup-engineering-harness npm executable and package invariants
• add a self-hosted Claude Code Marketplace/plugin manifest
• add provider-native Codex and Claude Code bridges, hooks, canaries, and audits
• add CI plus npm, installer, provider, and distribution tests
• update the canonical setup and installation documentation

Verification

• Python unittest suite: 188 passed
• npm CLI tests: 3 passed
• Agent Skill validation: passed
• Claude Code marketplace strict validation: passed on 2.1.212 and 2.1.220
• local and remote-branch Claude marketplace add/install/cache smoke tests: passed
• npm publish dry-run and packed-tarball execution: passed
• GitHub Actions CI on hosted Python/Node runtimes: passed

CI compatibility hardening

• GitHub-hosted Python and Node live under /opt/hostedtoolcache
• the verifier now allowlists precise Python sysconfig directories and the selected hosted tool version root, without exposing sibling tool-cache data
• regression tests cover both hosted-runtime access and sibling-secret isolation

Release gates

• npm registry publication requires an authenticated npm account
• a provider-attested live Claude canary requires Claude Code authentication
• Anthropic's official marketplace submission is a separate authenticated review step