feat(button,media_player): Pair ADB carries entity_category CONFIG (t30 G11) + BrowseMediaSource domain parameter at root and children (t30 G18, 2026-05-20 blog contract); stubs/tests pin both

tests/test_command_routing.py

@@ -971,6 +971,10 @@ class TestBrowseMediaDirectory:
             ("com.netflix.ninja", "Netflix"),
         ]
         assert all(c.media_content_type == "app" for c in root.children)
+        # t30 G18 (2026-05-20 blog): the domain parameter is present at
+        # every level of the tree
+        assert root.domain == "nvidia_shield"
+        assert all(c.domain == "nvidia_shield" for c in root.children)
 
     async def test_root_falls_back_to_the_curated_default(self, modules):
         player, _s, _i = make_player(modules)  # no apps map configured