chore: release v0.1.0-alpha.6

[chasechou007]

Summary

• prepare @echopath-labs/opendomain@0.1.0-alpha.6
• publish the Profile Runtime v1 changelog entry
• add the project-specific release and rollback runbook
• upgrade minimatch to 10.2.5 and align supported Node.js releases
• run CI on Node.js 20 and 22

Validation

• Node.js 20: 107 tests, 24-document validation, installed-package smoke passed
• Node.js 22: 107 tests, 24-document validation, installed-package smoke passed
• npm audit: 0 vulnerabilities
• package dry-run: 56 entries, 71,763 bytes
• OpenSpec validation: 7/7

Release boundary

This PR prepares the source release only. npm publishing, the Git tag, and the GitHub prerelease will happen from the merged main commit after registry preflight. The alpha dist-tag will move to alpha.6; latest will remain unchanged.