Add per-child daily count and percentage sensors

Four sensors per active child read the coordinator snapshot: quests
due today (carrying the panel payload that omits missed instances plus
the admin payload that includes them, D-009), completed, remaining, and
completion percentage (100 on a zero-quest day). Platform forwarding
wired through the harness's entity registry stand-ins.

tests/test_const.py

@@ -28,10 +28,10 @@ def test_logger() -> None:
 
 
 def test_platforms() -> None:
-    """Verify PLATFORMS is defined as an empty list."""
+    """Verify PLATFORMS is defined as the sensor platform list."""
     assert hasattr(const, "PLATFORMS")
     assert isinstance(const.PLATFORMS, list)
-    assert const.PLATFORMS == []
+    assert const.PLATFORMS == ["sensor"]
 
 
 def test_sqlite_db_filename() -> None: