feat(vscode): v0.1.1 — docs overhaul + GitHub Release pipeline (#6)

- Rewrite Marketplace README with a full .mdv format tour: front-matter,
  fenced chart/table/stat blocks, ::: containers, auto TOC, all chart types,
  styled regions, two-column layout, non-goals, troubleshooting.
- Bump extension to 0.1.1; update CHANGELOG.
- Replace publish-vscode.yml with release-vscode-extension.yml that builds
  the .vsix and attaches it to a GitHub Release (no Marketplace PAT kept on
  GitHub). Triggered by vscode-v* tags or workflow_dispatch.
- Update docs/publishing-vscode-extension.md with the new flow.