chore: trigger releases from main changesets

[marandaneto]

💡 Motivation and Context

Standardize SDK releases so they are triggered by pushes to main containing release changesets, rather than by PR labels or pull_request.closed events.

Changes

• Updated the release workflow to run on push to main for .changeset/**, while keeping manual workflow_dispatch
• Removed release-label and bump-label checks from the release flow
• Added [skip ci] to release version-bump commits and narrowed release path filters to changeset markdown files to avoid re-triggering release workflows on consumed changeset deletions
• Updated only the release-label parts of the release docs and PR checklist

💚 How did you test it?

• Parsed the updated release workflow YAML locally
• Verified the release workflow no longer references pull_request, PR labels, or bump labels
• Verified PR templates no longer ask for release labels

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file (not needed for this release-process-only change)

[greptile-apps]

_{Reviews (1): Last reviewed commit: "chore: skip release workflow on version ..." | Re-trigger Greptile}