No browser chosen, no "Open on" button

The plain address is the one thing that button must not offer -- followed
in the browser the rewrite rules are installed in, it comes straight back
here -- so there is nothing to show until there is a browser to hand it to.
The copy button and the selectable URL were always the part carrying the
weight; the open link now ships hidden and the script reveals it along with
the scheme.

That also settles what the button should say. It went back to "Open on
<platform>": the browser's name was there to explain a tap that went
nowhere, and a button that is not shown until it works needs no such
explanation.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01KF5YF3iZVKbezwALap8LYd

test/render.test.ts

@@ -105,8 +105,12 @@ test('a failure still hands the link back', () => {
     detail: 'TikTok showed a verification puzzle instead of the post.',
   });
   assert.ok(page.includes('data-url="https://www.tiktok.com/@a/video/1"'));
-  assert.ok(page.includes('Open on TikTok'));
+  assert.ok(page.includes('<code>https://www.tiktok.com/@a/video/1</code>'));
   assert.ok(page.includes('verification puzzle'));
+  // Following the original link in the browser the rewrite rules are
+  // installed in only comes back here, so it stays hidden until the script
+  // has a browser to hand it to.
+  assert.ok(/<a class="original__open"[^>]* hidden>Open on TikTok<\/a>/.test(page));
 });
 
 function redditPost(overrides: Partial<Post> = {}): Post {