Remove react-router dependency

[Copilot]

Removes react-router entirely (both the CDN script and the npm dependency) in favor of minimal native hash-based routing.

Changes

• script.jsx

  • Added getHashParams() to parse window.location.hash into { scriptId, action }
  • Dropped ReactRouter.State mixin from Script, Line, and Nav; replaced all this.getParams() calls with getHashParams()
  • Replaced <Link to="/demo"> with <a href="#/demo">
  • Replaced ReactRouter.run() + Route/DefaultRoute/RouteHandler bootstrap with a simple App component rendered on hashchange

  function getHashParams() {
    var hash = window.location.hash.replace(/^#\/?/, '');
    var parts = hash ? hash.split('/') : [];
    return { scriptId: parts[0] || null, action: parts[1] || null };
  }
  
  window.addEventListener('hashchange', renderApp);
  renderApp();

• index.html — removed react-router@0.11.6 CDN <script> tag

• package.json — removed "react-router": "^7.13.0" from dependencies