Stop every test page asking for a favicon nothing serves

`ready()` waits for the network to go idle, and each probe page asked for
/favicon.ico, which its route does not answer: the server threw
NotFoundHttpException on the way, and on the runner the two full-screen
date picker tests spent their whole budget inside that wait rather than
in the click Pest named. Every probe page now carries `<link rel="icon"
href="data:,">`, so the browser asks for nothing.

The showcase's own head carries it too. It ships no icon, and the 404 was
the application's to answer.

The runner takes two and a half to three times as long as a workstation,
so BROWSER_TIMEOUT there goes from 15 to 45 seconds: a page that loads
the application's Vite entries, Alpine and Livewire had no headroom left.

Feature 1159 passed; Browser 299 passed on Chrome, Firefox and WebKit.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

resources/views/showcase/head.blade.php

@@ -7,6 +7,10 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover" />
     <meta name="robots" content="noindex" />
 
+    {{-- The showcase is the package's own page and ships no icon: an empty data URI keeps the
+         browser from asking the application for /favicon.ico, which its routes need not answer. --}}
+    <link rel="icon" href="data:," />
+
     <title>{{ $pageTitle }}</title>
 
     <x-livewire-material::theme-script />