play-probe: report branch + browser capabilities on every play attempt

iPhone stays on 'Loading…' with zero /stream requests and no error
event — impossible under any known code path, so instrument the
branch decision itself: which branch (hlsjs/native/none-throw),
hls.js presence, MSE support, native-HLS capability, full UA.

static/index.html

@@ -6,7 +6,7 @@
 <title>ani-web</title>
 <link rel="icon" href="data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 64 64'%3E%3Crect width='64' height='64' rx='14' fill='%23f97316'/%3E%3Ctext x='32' y='45' font-family='sans-serif' font-size='42' font-weight='700' text-anchor='middle' fill='%230e0f13'%3Ea%3C/text%3E%3C/svg%3E">
 
-<link rel="stylesheet" href="style.css?v=8">
+<link rel="stylesheet" href="style.css?v=9">
 </head>
 <body>
 <header>
@@ -30,6 +30,6 @@
      max-age=300 in browser AND possibly in your HTTPS proxy, and a stale
      copy is exactly how users keep seeing an old UI after a deploy -->
 <script src="hls.min.js"></script>
-<script src="app.js?v=8"></script>
+<script src="app.js?v=9"></script>
 </body>
 </html>