parse_device0_batch used to collapse /device/0's {"href": "..."} "no data
yet" marker into a plain {}, indistinguishable from a resource the device
had actually polled and confirmed empty. Every exists_fn using the "not
rep or ..." stub carve-out (and entity._is_included's default field-gate)
then treated both the same way, creating phantom always-"unknown" entities
for any resource a model simply doesn't support (e.g. GSzabados's fridge's
/energy/consumption/vs/0).
is_stub_rep() now recognizes only the literal {"href": ...} marker as a
stub; a genuine {} is treated as the device's real (if empty) answer and
gates the entity off like any other missing field. Updated the energy
meter, self-check error, cooktop burner, and range-hood auto-operation
exists_fn call sites, plus three golden fixtures that had baked the
phantom-entity behavior in as "expected".
