Never end playback over the cosmetic surround; always shut down OpenVR

Review (SWE-2 Max): a non-standby error re-sending the theatre surround
could end a healthy still, and a non-RuntimeError during DestroyOverlay
skipped VR_ShutdownInternal. drain() now drops a surround that fails for
other reasons, and close() shuts down in finally. Fake overlay handles no
longer depend on call order.

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

tests/test_media.py

@@ -81,8 +81,12 @@ class Media(unittest.TestCase):
             write_status(path, **values)
 
         class FakeOverlay:
+            created = 0
+
             def create(self, *a, **k):
-                return len(calls)
+                # Handles in creation order: surround 0, then screen 1 (theatre).
+                FakeOverlay.created += 1
+                return FakeOverlay.created - 1
 
             def call(self, *a):
                 pass