fix: load /login instead of root so premature auth detection is prevented

Loading https://claude.ai as the start URL caused didFinish to fire on
the landing page while stale/tracking cookies were already in
WKWebsiteDataStore. The 'any claude.ai cookie' check then fired
immediately, closing the login sheet before the user could sign in.

Loading /login ensures the URL-guard catches the initial page load and
only checks cookies after the real post-login redirect.

ClaudeChecker/LoginView.swift

@@ -12,7 +12,7 @@ struct LoginWebView: NSViewRepresentable {
 
         let webView = WKWebView(frame: .zero, configuration: config)
         webView.navigationDelegate = context.coordinator
-        webView.load(URLRequest(url: URL(string: "https://claude.ai")!))
+        webView.load(URLRequest(url: URL(string: "https://claude.ai/login")!))
         return webView
     }