De-duplicate the legacy ARTIK051 AC board-generation test (#161)

capabilities/airconditioner.py's is_legacy_board() (renamed from the
private _is_legacy_board -- it's now a cross-module helper) and
climate.py's _legacy_airflow() implemented the same "does this board have
/airflow/vs/0 but no /wind/strength/vs/0" test independently, one via
literal href strings and the other via coordinator.resource() truthiness.
is_legacy_board() now uses the module's own HREF_AIRFLOW/HREF_WIND_STRENGTH
constants, and _legacy_airflow() delegates to it via a minimal two-key
presence dict (cheaper than a full last_resources snapshot copy) instead of
re-implementing the check, so the token entities and the climate card's
legacy read/write paths can't drift apart on which board generation is in
play.

tests/test_airconditioner_artik051_krac.py

@@ -24,7 +24,8 @@ from custom_components.localthings.registry.by_type import (
     airconditioner, for_device_by_model,
 )
 from custom_components.localthings.registry.capabilities.airconditioner import (
-    HREF_AIRFLOW, _option_number_write, _option_switch_write,
+    HREF_AIRFLOW, HREF_WIND_STRENGTH, _option_number_write,
+    _option_switch_write, is_legacy_board,
 )
 from custom_components.localthings.registry.discovery import discover
 from custom_components.localthings.registry.entities import ClimateDesc
@@ -119,6 +120,22 @@ def test_token_entities_stay_off_newer_boards():
         assert key not in state, key
 
 
+def test_climate_legacy_airflow_gate_agrees_with_is_legacy_board():
+    """issue #161: climate.py's _legacy_airflow() delegates to
+    capabilities/airconditioner.py's is_legacy_board() instead of
+    re-implementing the same presence/absence check, so the token entities
+    and the climate card's legacy read/write paths can't drift apart on
+    which board generation is in play."""
+    legacy_resources = _load_device(FIXTURE)
+    assert is_legacy_board(legacy_resources) is True
+    assert _climate(legacy_resources)._legacy_airflow() == legacy_resources[HREF_AIRFLOW]
+
+    newer_resources = _load_device('airconditioner_tp1x_rac')
+    assert is_legacy_board(newer_resources) is False
+    assert _climate(newer_resources)._legacy_airflow() == {}
+    assert HREF_WIND_STRENGTH in newer_resources
+
+
 def test_absent_token_yields_no_entity():
     """The issue #136 unit of this same model reports no Spi token."""
     resources = _load_device(FIXTURE)