Auto-trigger release pipeline on main merge and add version check

[msyyc]

Changes

• publish-release.yml: Changed from manual trigger ( rigger: none) to automatic trigger on main branch merges. Added a version check step that verifies packages are not already published before proceeding with the build, tests, and publish.
• README.md: Updated release documentation to reflect that the pipeline is now triggered automatically after merge.

Why

This removes the manual step of triggering the release pipeline after a release PR is merged, making the release process more streamlined and less error-prone. The version check guard ensures the pipeline exits early if the versions are already published.