Fix ty type-check failures in new tests (CI)

My local ty runs only covered custom_components, not tests -- CI runs
'ty check custom_components tests', which this branch had been failing
since the version-bump commit. All 13 diagnostics were the same two
established idioms this test suite already uses elsewhere, just missing
here:

- desc.write_fn/options_field are SelectDesc-only fields, unresolved on
  the SamsungEntityDescription base a bare 'next(e for e in ... if
  e.key == ...)' infers -- needs 'and isinstance(e, SelectDesc)' in the
  filter, same as test_fridge_capabilities.py's existing selects.
- rep_fn/match_fn are typed Optional even after narrowing to a concrete
  descriptor/capability, so calling one needs an explicit
  'assert x.rep_fn is not None' first, same as
  test_common_capabilities.py's POWER_VS_FALLBACK.match_fn precedent.

No behavior change -- test bodies are identical, just type-checkable.

tests/test_airconditioner_capabilities.py

@@ -784,6 +784,7 @@ def test_air_filter_usage_hours_derived_from_percent_and_capacity():
         for e in airconditioner.AIR_FILTER.entities
         if e.key == "air_filter_usage_hours" and isinstance(e, SensorDesc)
     )
+    assert desc.rep_fn is not None
     assert (
         desc.rep_fn(
             {"x.com.samsung.da.filterUsage": "91", "x.com.samsung.da.filterCapacity": "500"}

tests/test_refrigerator_tp1x_ref_21k_autodoor_capabilities.py

@@ -10,6 +10,7 @@ from custom_components.localthings.registry.adapter import flatten
 from custom_components.localthings.registry.by_type import for_device_by_model
 from custom_components.localthings.registry.capabilities import fridge
 from custom_components.localthings.registry.discovery import discover
+from custom_components.localthings.registry.entities import SelectDesc
 from tests.conftest import _load_device
 
 FIXTURE = "refrigerator_tp1x_ref_21k_autodoor"
@@ -51,7 +52,11 @@ def test_auto_door_voice_control_reads_status_lock():
 
 
 def test_auto_door_timer_reads_its_own_options():
-    desc = next(e for e in fridge.AUTO_DOOR_TIMER.entities if e.key == "auto_door_timer")
+    desc = next(
+        e
+        for e in fridge.AUTO_DOOR_TIMER.entities
+        if e.key == "auto_door_timer" and isinstance(e, SelectDesc)
+    )
     rep = {
         "x.com.samsung.da.time.desired": "1",
         "x.com.samsung.da.time.supportedOptions": ["1", "2", "3", "4", "5", "6"],
@@ -70,5 +75,6 @@ def test_auto_door_single_variant_href_bound_with_no_entities():
     no paired current/desired field to expose, so it's coverage-only via
     the shared AUTO_DOOR_VARIANT pattern cap, not an entry of its own."""
     assert fridge.AUTO_DOOR_VARIANT.entities == ()
+    assert fridge.AUTO_DOOR_VARIANT.match_fn is not None
     _reg, resources = _fridge()
     assert fridge.AUTO_DOOR_VARIANT.match_fn(resources["/autodoor/single/vs/0"], resources)

tests/test_refrigerator_tp1x_ref_21k_kimchi_capabilities.py

@@ -52,5 +52,6 @@ def test_auto_door_opener_present():
 
 def test_auto_door_kimchi_variant_href_bound_with_no_entities():
     assert fridge.AUTO_DOOR_VARIANT.entities == ()
+    assert fridge.AUTO_DOOR_VARIANT.match_fn is not None
     _reg, resources = _fridge()
     assert fridge.AUTO_DOOR_VARIANT.match_fn(resources["/autodoor/kimchi/vs/0"], resources)

tests/test_refrigerator_winecellar_capabilities.py

@@ -10,6 +10,7 @@ from custom_components.localthings.registry.adapter import flatten
 from custom_components.localthings.registry.by_type import for_device_by_oic_type, resolve
 from custom_components.localthings.registry.capabilities import fridge
 from custom_components.localthings.registry.discovery import discover
+from custom_components.localthings.registry.entities import SelectDesc
 from tests.conftest import _load_device
 
 FIXTURE = "refrigerator_winecellar"
@@ -67,7 +68,9 @@ def test_deodor_filter_has_its_own_keys_not_air_filters():
 
 def test_winecellar_pantry_zone_mode_options_and_write():
     desc = next(
-        e for e in fridge.WINECELLAR_PANTRY_ZONE.entities if e.key == "winecellar_pantry_zone_mode"
+        e
+        for e in fridge.WINECELLAR_PANTRY_ZONE.entities
+        if e.key == "winecellar_pantry_zone_mode" and isinstance(e, SelectDesc)
     )
     assert desc.options_field == "x.com.samsung.da.supportedOptions"
     assert desc.write_fn is not None
@@ -82,5 +85,6 @@ def test_winecellar_pantry_zone_mode_options_and_write():
 def test_winecellar_variant_and_info_hrefs_bound_with_no_entities():
     assert fridge.AUTO_DOOR_VARIANT.entities == ()
     assert fridge.WINECELLAR_INFO.entities == ()
+    assert fridge.AUTO_DOOR_VARIANT.match_fn is not None
     _reg, resources = _fridge()
     assert fridge.AUTO_DOOR_VARIANT.match_fn(resources["/autodoor/winecellar/vs/0"], resources)