Add connector release contract tooling

[tnunamak]

Summary

• add the canonical connector-index v2 schema and release publication workflow
• expand installer tooling with lock generation, install, update, prune, and verify helpers
• ship a CLI entrypoint and document the new artifact/index distribution contract

Validation

• node --input-type=module -e "import('./packages/connector-installer-core/index.mjs').then(() => console.log('ok'))"
• node ./packages/connector-installer-cli/index.mjs
• node ./scripts/generate-connector-index.mjs
• node ./scripts/generate-connector-index.mjs --check

[github-actions]

Schema Health Check — Non-blocking inherited issues

41/47 scopes consistent | 6 inherited Gateway gap(s) | no new blocking issues in this PR