Mac in the headset: end the Frame's viewer browser after Stop; relay fixes

- Chromium on the Frame outlived its last viewer window (verified: 11
  processes left after a run). Once nothing is shown, Stop ends it, unless
  Show was pressed again meanwhile; its profile is Frame Control's own.
- Relay --delay: if the agent side fails, close the viewer side too
  (review round 9).
- Docs: the final scroll run captured 57 fps; don't blame ScreenCaptureKit.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/test_macview.py

@@ -19,6 +19,7 @@ import sys
 import tempfile
 import time
 import unittest
+from unittest import mock
 from pathlib import Path
 
 ROOT = Path(__file__).resolve().parent.parent
@@ -82,6 +83,22 @@ class Helpers(unittest.TestCase):
             mv.show("display:1")
         self.assertIn("Screen Recording", str(cm.exception))
 
+    def test_stop_all_ends_the_viewer_browser_unless_shown_again(self):
+        calls = []
+        mv = frame_macview.MacView(["ssh"], lambda remote, **kw: calls.append(remote) or "", "frame")
+        mv.agent = mock.Mock(poll=lambda: None)
+        mv.call = lambda path, **kw: {"closed": 1}
+        mv.shown = {"window:5"}
+        with mock.patch.object(frame_macview.time, "sleep"):
+            gen = mv.shows
+            mv.shown.clear()
+            mv._end_viewer_browser(gen)
+            self.assertEqual(len(calls), 1)
+            self.assertIn("pkill -f '[f]rame-control/mac-view", calls[0])
+            mv.shows += 1  # Show pressed during the wait: leave the new viewer alone
+            mv._end_viewer_browser(gen)
+            self.assertEqual(len(calls), 1)
+
 
 class WS:
     """A minimal WebSocket client (masked frames out, plain frames in)."""