Add GA4 header_link_click event to GitHub nav link

[Copilot]

Fires a GA4 event when the GitHub star button in the site header is clicked, enabling tracking of header CTA engagement.

Changes

• custom.d.ts — Augments Window with an optional gtag type so the call compiles without errors
• components/AppNavBar.tsx — Adds onClick to both the desktop and mobile GitHubStarButton <Link> instances:

window.gtag?.('event', 'header_link_click', {
  link_name: 'GitHub',
  link_url: `https://github.com/${item.owner}/${item.repo}`,
  location: 'header',
});

Mobile handler preserves the existing closeMenu() call. Link target="_blank" behavior is unchanged.

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• Have you followed the guidelines in our Contributing document?
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Project	Deployment	Actions	Updated (UTC)
tina-io	Ready	Preview	Jul 29, 2026 9:19pm