Move the on/off interpretation into a single remote_control_enabled()
in registry/capabilities/common.py so the write-guard added in the
previous commit can't silently drift from the Smart Control binary
sensor's own reading of the same hrefs. Also promotes both
/remotectrl hrefs to poll_tier='warm' so the coordinator's cached
state backing that write guard doesn't lag up to a full 30s cold
summary poll behind the device's actual toggle state.