Distinguish not-yet-fetched stub reps from confirmed-empty ones (issue #127)

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".

tests/test_batch.py

@@ -0,0 +1,56 @@
+"""Tests for registry.batch — the /device/0 sweep parser and its stub marker.
+
+issue #127: a device whose /energy/consumption/vs/0 is permanently
+unsupported reports a genuinely empty {} rep for it. The previous parser
+collapsed /device/0's own {"href": "..."} "not fetched yet" marker to that
+same {} shape, so downstream exists_fn checks couldn't tell "confirmed
+empty" apart from "haven't polled it yet" and created phantom always-
+"unknown" entities either way. is_stub_rep/parse_device0_batch now keep the
+two shapes distinct.
+"""
+from custom_components.localthings.registry.batch import is_stub_rep, parse_device0_batch
+
+
+class TestIsStubRep:
+    def test_true_for_bare_href_marker(self):
+        assert is_stub_rep({'href': '/energy/consumption/vs/0'}) is True
+
+    def test_false_for_genuinely_empty_rep(self):
+        assert is_stub_rep({}) is False
+
+    def test_false_for_populated_rep(self):
+        assert is_stub_rep({'x.com.samsung.da.cumulativePower': '58900'}) is False
+
+    def test_false_for_href_plus_data(self):
+        """A real, populated rep may legitimately echo 'href' alongside
+        actual fields -- only a rep with *no other keys* is the stub."""
+        assert is_stub_rep({'href': '/x/0', 'value': True}) is False
+
+
+class TestParseDevice0Batch:
+    def test_stub_rep_kept_distinct_from_genuine_empty(self):
+        device0 = [
+            {},
+            {'href': '/energy/consumption/vs/0', 'rep': {'href': '/energy/consumption/vs/0'}},
+            {'href': '/sabbath/vs/0', 'rep': {}},
+        ]
+        resources = parse_device0_batch(device0)
+        assert is_stub_rep(resources['/energy/consumption/vs/0']) is True
+        assert is_stub_rep(resources['/sabbath/vs/0']) is False
+        assert resources['/sabbath/vs/0'] == {}
+
+    def test_populated_rep_passes_through_unchanged(self):
+        device0 = [
+            {},
+            {'href': '/door/cooler/0', 'rep': {'openState': 'Close'}},
+        ]
+        resources = parse_device0_batch(device0)
+        assert resources['/door/cooler/0'] == {'openState': 'Close'}
+
+    def test_skips_entries_without_href(self):
+        device0 = [{}, {'rep': {'a': 1}}]
+        assert parse_device0_batch(device0) == {}
+
+    def test_skips_non_dict_rep(self):
+        device0 = [{}, {'href': '/x/0', 'rep': 'not-a-dict'}]
+        assert parse_device0_batch(device0) == {}