Stop collapsing a genuine fivepercentHumidity=0 reading to unknown (#160)

#146's zero-as-"not measuring" carve-out was meant for ARTIK051 boards'
plain x.com.samsung.da.humidity field, which only populates while Air
monitoring is briefly on and zeroes out afterward. It was accidentally
applied to fivepercentHumidity too, which every other AC board relies on
and which has never been documented getting stuck at zero -- so a real 0%
reading on those boards silently became "unknown". Only the humidity
fallback field now collapses 0; fivepercentHumidity passes 0 through as a
real reading.

custom_components/localthings/registry/capabilities/airconditioner.py

@@ -210,14 +210,20 @@ def _humidity(rep):
     (51% observed, matching what the same unit's cloud integration reported at
     that moment), then zeroes the field and switches Air monitoring back off by
     itself. So 0 reads as "not measuring" and is reported as unknown rather than
-    as 0% humidity, which would poison long-term history -- which is also why
-    the boards that do have fivepercentHumidity read a permanent 0 here.
+    as 0% humidity, which would poison long-term history.
+
+    That zero-as-"not measuring" carve-out is specific to the ARTIK051
+    fallback field's hardware quirk -- every other board's fivepercentHumidity
+    has never been documented getting stuck at zero, and collapsing a
+    genuine 0% reading there to unknown is a regression, not a safeguard
+    (issue #160). So fivepercentHumidity passes 0 through unchanged; only the
+    humidity fallback applies the zero-collapse.
     """
-    for field in ('x.com.samsung.da.fivepercentHumidity',
-                  'x.com.samsung.da.humidity'):
-        if field in rep:
-            value = _num(rep[field])
-            return value if value else None
+    if 'x.com.samsung.da.fivepercentHumidity' in rep:
+        return _num(rep['x.com.samsung.da.fivepercentHumidity'])
+    if 'x.com.samsung.da.humidity' in rep:
+        value = _num(rep['x.com.samsung.da.humidity'])
+        return value if value else None
     return None