Shortify browser extension

The same ZIP works in Google Chrome and Microsoft Edge. Both use the Chromium
extension format. Chrome 114 or newer is required for the side panel.

1. Open chrome://extensions in Chrome, or edge://extensions in Edge.
2. Turn on Developer mode.
3. Choose Load unpacked.
4. Select this browser-extension folder.
5. Pin Shortify, open an article, and click the toolbar icon.
6. The story opens in the side panel, sized like a phone, with the article
   dimmed behind it. Click **Shortify this article** to prepare one; an
   article that already has a story opens straight into it. Use Save or Share
   at the top of the story; sharing also keeps the public story link. If
   preparation is still running, close the panel and return later to resume.

The panel stays open while you switch tabs, so stepping away to fetch an
email sign-in code does not lose your place.

The extension sends only the active article URL to Shortify's /plugin route.
