ci: convert to auto-publish on merge to main

[vorflux]

Summary

Converts the publish workflow from tag-based (v* tags) to auto-publish on merge to main when package.json changes.

Changes

• Updated .github/workflows/release.yml:
  • Trigger changed from push: tags: ['v*'] to push: branches: [main], paths: ['package.json']
  • Added actions/setup-node@v4 with registry-url for proper npm auth
  • Added version-check step that compares against npm registry before publishing
  • Added id-token: write permission for npm provenance (OIDC trusted publishing)
  • Added NPM_CONFIG_PROVENANCE: true to publish step

Workflow features

• Trigger: Push to main with package.json path filter
• Version check: Skips publish if version already exists on npm
• Quality gates: Runs typecheck and build before publishing
• npm trusted publishing: OIDC provenance support

Testing

This is a CI workflow file change -- validated YAML syntax locally. The workflow will be tested on the first merge to main that bumps the version in package.json.

---

Session Details

• Session: View Session
• Requested by: Dhravya Shah (dhravya@supermemory.com)
• Address comments on this PR. Add (aside) to your comment to have me ignore it.