Stop surfacing '_OFF'-suffixed placeholder alarm codes (#166)

Samsung pre-populates /alarms/vs/0 with one row per supported alarm type,
each carrying a '<Name>_OFF' placeholder code (no 'Deleted' state at all)
when that alarm isn't firing. common._active_alarm_codes only ever
filtered on 'Deleted' state, so every device using this shared capability
(including the AC family) showed these inert placeholders --
'ErrorCode_OFF', 'FilterAlarm_OFF' -- as if they were live alarms.

Confirmed the '_OFF' suffix convention holds across every alarm code seen
in this repo's fixtures so far (ErrorCode_OFF, FilterAlarm_OFF, OV_E_OFF,
CT_E_OFF, WaterTankFull_OFF, AC_V_0002_OFF, all placeholders; DoorA_Opened,
FilterAlarm, SNSF_Reached, all genuinely active with no suffix) -- issue
#166's own dump has both a FilterAlarm_OFF placeholder and, on a second
unit, a live FilterAlarm/state=Created alert, which is what motivated
generalizing range_hood.py's existing (but narrower, ErrorCode_OFF-only)
special case into the shared helper instead of duplicating it further.

The other three points in #166 (filter-usage percentage vs. filterStatus
disagreement, an "air purification" config toggle the reporter says has no
physical effect, a "beep on/off" control) don't have a confirmed code fix:
the percentage math already matches the device's own filterUsage/
filterCapacity fields (filterStatus is a separate device-computed field we
already relay verbatim, not something we derive), the air-purify resource
is correctly wired to what the board reports and its absence from the
official app's own options list suggests an inert shared-board-profile stub
rather than an integration bug, and a "Beep volume" NumberDesc keyed off
the same Volume_100 option both dumps report already exists (0 mutes it).

custom_components/localthings/registry/capabilities/common.py

@@ -91,12 +91,25 @@ def _ml_to_l(v):
 
 
 def _active_alarm_codes(items):
-    """Join active alarm codes; skip retained rows Samsung leaves as Deleted.
+    """Join active alarm codes; skip retained rows Samsung leaves as Deleted,
+    and any code ending in '_OFF'.
 
     Laundry boards keep a Deleted ErrorCode row in /alarms/vs/0 after the
     condition clears (see WD7000B diagnostics). Surface only live alarms so
-    HA doesn't stick on a stale ErrorCode. Range-hood has its own stricter
-    helper that also drops ErrorCode_OFF.
+    HA doesn't stick on a stale ErrorCode.
+
+    Samsung pre-populates this array with one row per alarm *type* the board
+    supports, each carrying its own '<Name>_OFF' placeholder code when that
+    alarm isn't firing -- confirmed across independent device families
+    (ErrorCode_OFF, FilterAlarm_OFF, OV_E_OFF, CT_E_OFF, WaterTankFull_OFF,
+    AC_V_0002_OFF all appear in fixtures with no corresponding active
+    condition). An alarm that's actually firing instead reports a plain,
+    unsuffixed code (FilterAlarm, DoorA_Opened, SNSF_Reached) -- issue #166's
+    AC dump has both a FilterAlarm_OFF placeholder and shows what a live
+    filter alert looks like: code 'FilterAlarm' (no suffix), state
+    'Created'. Range-hood previously special-cased only the literal
+    'ErrorCode_OFF' string in its own stricter helper; this generalizes
+    the same rule to the whole '_OFF' suffix convention.
     """
     if not items or not isinstance(items, list):
         return 'none'
@@ -105,6 +118,7 @@ def _active_alarm_codes(items):
         for i in items
         if i.get('x.com.samsung.da.code')
         and str(i.get('x.com.samsung.da.state', '')).lower() != 'deleted'
+        and not str(i.get('x.com.samsung.da.code', '')).lower().endswith('_off')
     ]
     return ', '.join(codes) if codes else 'none'