fix(release): correct package identifier and restore GitHub Release step

- Revert workflow to use internal identifier 'llmx' instead of scoped name
- Revert build_npm_package.py to only accept internal identifiers
- Restore "Create GitHub Release" step that was incorrectly removed
- Package name '@valknarthing/llmx' is read from package.json by the script

This matches OpenAI's approach where they use 'codex' not '@openai/codex' in workflow.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/rust-release.yml

@@ -447,6 +447,16 @@ jobs:
             --release-version "${{ steps.release_name.outputs.name }}" \
             --package llmx
 
+      - name: Create GitHub Release
+        uses: softprops/action-gh-release@v2
+        with:
+          name: ${{ steps.release_name.outputs.name }}
+          tag_name: ${{ github.ref_name }}
+          files: dist/**
+          # Mark as prerelease only when the version has a suffix after x.y.z
+          # (e.g. -alpha, -beta). Otherwise publish a normal release.
+          prerelease: ${{ contains(steps.release_name.outputs.name, '-') }}
+
       - uses: facebook/dotslash-publish-release@v2
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}