Rework AIComfort as an HVACMode.AUTO + preset overlay, add unmapped-mode warning (issue #93)

AIComfort isn't a distinct thermodynamic operation like Cool/Dry/Heat --
it's an AI-driven overlay on top of the device's own 'Auto' behavior,
confirmed by A-CAWW-TP2-20-COMMON reporting both 'Auto' and 'AIComfort'
as separate, mutually-exclusive entries in /mode/vs/0's supportedModes.
Modeled the idiomatic HA way instead of a flat _DEVICE_TO_HVAC entry:
hvac_mode reports AUTO and a new 'ai_comfort' preset carries the
distinction. Entered/left only via the preset (writes the primary mode
resource, not the convenient one) -- there's no dedicated HVACMode
value for it, so it's not offered in the hvac_mode dropdown directly.

Also adds a once-per-(href, code) warning log when a device-reported
mode has no entry in the relevant map, so a future gap like this one
surfaces in the log instead of silently vanishing -- the exact failure
mode issue #93 called out ("this class of gap is invisible without
diffing against supportedModes").

tests/test_climate_ac_modes.py

@@ -1,34 +1,40 @@
-"""Tests for the AC HVAC-mode device<->HA map in climate.py (issue #93).
+"""Tests for the AC HVAC-mode/preset device<->HA maps in climate.py (issue #93).
 
-`_DEVICE_TO_HVAC`/`_HVAC_TO_DEVICE` are plain module-level dicts with no
-coordinator/entity dependency, so -- like `_temps_vs_item` in
-test_climate_temperature_fallback.py -- they're testable directly.
+Module-level dicts/constants with no coordinator/entity dependency, so --
+like `_temps_vs_item` in test_climate_temperature_fallback.py -- they're
+testable directly.
 """
 from homeassistant.components.climate import HVACMode
 
-from custom_components.localthings.climate import _DEVICE_TO_HVAC, _HVAC_TO_DEVICE
-
-
-def test_aicomfort_maps_to_auto():
-    """A-CAWW-TP2-20-COMMON (issue #93) reports 'AIComfort' in its
-    supportedModes alongside 'Auto' -- a separate AI-driven auto-comfort
-    mode, distinct from the existing 'Auto' -> HEAT_COOL entry."""
-    assert _DEVICE_TO_HVAC['AIComfort'] == HVACMode.AUTO
+from custom_components.localthings.climate import (
+    _AI_COMFORT_MODE, _DEVICE_TO_HVAC, _HVAC_TO_DEVICE, PRESET_AI_COMFORT,
+)
 
 
 def test_auto_still_maps_to_heat_cool():
-    """'AIComfort' is additive -- the existing 'Auto' -> HEAT_COOL mapping
-    (a different device code) is unchanged."""
+    """'Auto' is unchanged -- AIComfort is handled separately, not folded
+    into this map."""
     assert _DEVICE_TO_HVAC['Auto'] == HVACMode.HEAT_COOL
 
 
-def test_hvac_auto_writes_back_aicomfort():
-    """Reverse map: selecting HA's Auto hvac_mode writes the 'AIComfort'
-    device code, not 'Auto' (which is reserved for HEAT_COOL)."""
-    assert _HVAC_TO_DEVICE[HVACMode.AUTO] == 'AIComfort'
+def test_aicomfort_not_in_flat_hvac_map():
+    """AIComfort isn't a flat _DEVICE_TO_HVAC entry -- it's an AI overlay on
+    top of 'Auto', modeled as hvac_mode=AUTO + a dedicated preset instead of
+    a distinct HVACMode value (see the climate.py module comment)."""
+    assert _AI_COMFORT_MODE not in _DEVICE_TO_HVAC
+
+
+def test_hvac_auto_not_writable_via_hvac_mode():
+    """HVACMode.AUTO has no _DEVICE_TO_HVAC entry, so it's unreachable via
+    async_set_hvac_mode -- entered/left only through the ai_comfort preset."""
+    assert HVACMode.AUTO not in _HVAC_TO_DEVICE
 
 
 def test_fan_only_still_reachable_via_wind():
     """Guard against regressing the existing 'Wind' -> FAN_ONLY entry while
     editing this map."""
     assert _DEVICE_TO_HVAC['Wind'] == HVACMode.FAN_ONLY
+
+
+def test_preset_ai_comfort_constant():
+    assert PRESET_AI_COMFORT == 'ai_comfort'