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/entity_stublib.py

@@ -78,6 +78,7 @@ class BrowseMediaSource:
         media_content_id,
         can_play,
         can_expand,
+        domain=None,  # t30 G18 (2026-05-20 blog contract)
         children=None,
         thumbnail=None,
     ):
@@ -87,6 +88,7 @@ class BrowseMediaSource:
         self.media_content_id = media_content_id
         self.can_play = can_play
         self.can_expand = can_expand
+        self.domain = domain
         self.children = children or []
         self.thumbnail = thumbnail
 
@@ -287,6 +289,9 @@ def install() -> None:
     )
     entity = types.ModuleType("homeassistant.helpers.entity")
     entity.DeviceInfo = dict
+    entity.EntityCategory = types.SimpleNamespace(
+        CONFIG="config", DIAGNOSTIC="diagnostic"
+    )
     helpers.entity = entity
     entity_platform = types.ModuleType("homeassistant.helpers.entity_platform")
     entity_platform.AddEntitiesCallback = object