Deploy MathNote build to GitHub Pages

[aliorhun]

Summary

• add a GitHub Pages Actions workflow
• build the app before publishing instead of serving the source index.html
• publish only the generated dist/ directory
• run the offline verifier before deployment
• run build checks on pull requests without deploying them
• add .nojekyll to the generated distribution
• document the one-time Pages source setting

Why

The repository root index.html is now a build template containing MATHNOTE_BUILD_* markers. Publishing the repository root directly causes GitHub Pages to serve an HTML shell without the generated JS/CSS, so the UI does not initialize.

This workflow installs dependencies, builds dist/, verifies it, uploads it as a Pages artifact, and deploys that artifact after changes land on main.

One-time repository setting

In Settings → Pages → Build and deployment → Source, select GitHub Actions.

After that, merges to main deploy automatically to:
https://alorak.github.io/mathnote/