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.

custom_components/localthings/climate.py

@@ -51,6 +51,7 @@ from .registry.capabilities.airconditioner import (
     HREF_WIND_OSCILLATION as WIND_OSCILLATION_HREF,
     HREF_CONVENIENT as CONVENIENT_HREF,
     HREF_AIRFLOW as AIRFLOW_HREF,
+    is_legacy_board,
 )
 from .registry.capabilities.common import normalize_temp_unit
 
@@ -247,10 +248,23 @@ class LocalThingsClimate(LocalThingsEntity, ClimateEntity):
 
     def _legacy_airflow(self) -> dict:
         """The /airflow/vs/0 rep, but only when it is the fan/swing channel to
-        use -- i.e. this board has no /wind/strength/vs/0."""
-        if self.coordinator.resource(WIND_STRENGTH_HREF):
-            return {}
-        return self.coordinator.resource(AIRFLOW_HREF) or {}
+        use -- i.e. this board has no /wind/strength/vs/0.
+
+        Delegates the board-generation test to is_legacy_board (the same
+        test capabilities/airconditioner.py's token entities are gated on)
+        instead of re-implementing it, via a minimal presence dict built
+        from the two hrefs it actually inspects -- cheaper than
+        last_resources' full snapshot copy, since is_legacy_board only
+        checks key membership.
+        """
+        airflow = self.coordinator.resource(AIRFLOW_HREF)
+        wind_strength = self.coordinator.resource(WIND_STRENGTH_HREF)
+        presence = {}
+        if airflow:
+            presence[AIRFLOW_HREF] = airflow
+        if wind_strength:
+            presence[WIND_STRENGTH_HREF] = wind_strength
+        return airflow if is_legacy_board(presence) else {}
 
     def _legacy_preset(self) -> bool:
         """Whether presets come from the Comode_* token rather than a resource.

custom_components/localthings/registry/capabilities/airconditioner.py

@@ -152,7 +152,7 @@ def _option_token(rep, prefix):
     return None
 
 
-def _is_legacy_board(resources):
+def is_legacy_board(resources):
     """True for the board generation whose airflow lives in /airflow/vs/0.
 
     Newer families carry several of the same option tokens (Volume, Sleep,
@@ -163,13 +163,12 @@ def _is_legacy_board(resources):
     /airflow/vs/0. Same test as climate.py's _legacy_airflow(), so the entities
     below and the climate entity can never disagree about the generation.
     """
-    return ('/airflow/vs/0' in resources
-            and '/wind/strength/vs/0' not in resources)
+    return HREF_AIRFLOW in resources and HREF_WIND_STRENGTH not in resources
 
 
 def _has_option_token(prefix):
     return lambda rep, resources: (
-        _is_legacy_board(resources) and _option_token(rep, prefix) is not None)
+        is_legacy_board(resources) and _option_token(rep, prefix) is not None)
 
 
 def _option_token_on(prefix):