Stop the pinball engine from hijacking the browser tab's favicon

vpinball.js sets a table-supplied image as the page favicon via a blob:
URL as a table loads. Revert any blob: href on the icon <link> the
moment it appears, via a MutationObserver, instead of patching the
compiled engine.

lib/pinball/usePinballInstance.ts

@@ -61,6 +61,32 @@ export function usePinballInstance(
     const canvas = canvasRef.current;
     if (!canvas || !webgl2Supported) return;
 
+    // The engine sets a table-supplied image as the page favicon via a
+    // blob: URL (see vpinball.js's rel~='icon' link handling) — undesirable
+    // here, where the app's own favicon should stay put. Snapshot the
+    // current icon links up front and revert any blob: href the moment it
+    // appears, rather than patching the (compiled) engine itself.
+    const originalIconHrefs = new Map<HTMLLinkElement, string>();
+    document.querySelectorAll<HTMLLinkElement>("link[rel~='icon']").forEach((link) => {
+      originalIconHrefs.set(link, link.href);
+    });
+    const faviconObserver = new MutationObserver(() => {
+      document.querySelectorAll<HTMLLinkElement>("link[rel~='icon']").forEach((link) => {
+        if (!link.href.startsWith("blob:")) return;
+        const blobUrl = link.href;
+        const original = originalIconHrefs.get(link);
+        if (original) link.href = original;
+        else link.remove();
+        URL.revokeObjectURL(blobUrl);
+      });
+    });
+    faviconObserver.observe(document.head, {
+      childList: true,
+      subtree: true,
+      attributes: true,
+      attributeFilter: ["href"],
+    });
+
     setStatus("loading");
     const startedAt = performance.now();
 
@@ -103,6 +129,7 @@ export function usePinballInstance(
     })();
 
     return () => {
+      faviconObserver.disconnect();
       disposedRef.current = true;
       const instance = instanceRef.current;
       instanceRef.current = null;