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.

custom_components/nestquest/const.py

@@ -7,7 +7,9 @@ DOMAIN = "nestquest"
 LOGGER_NAME = "custom_components.nestquest"
 LOGGER = logging.getLogger(LOGGER_NAME)
 
-PLATFORMS: list[str] = []
+# Platforms set up per config entry (Feature 10): the per-child day
+# sensors. binary_sensor joins when task 4's entities land.
+PLATFORMS: list[str] = ["sensor"]
 
 #: Canonical domain-global service names (design/ENTITIES-AND-SERVICES.md §2
 #: plus the existing Feature 07 regenerate service).