HeadsetEcoMode: skip same-value writes to avoid G522 NACK 0x0B

RE of lghub_agent.arm64 revealed that LGHUB's service-layer handler
for 0x0618 HeadsetBatterySaverMode
(on_headset_battery_saver_set_handler @ 0x100c21790) compares the
requested new state against its cached current state and ONLY invokes
the devio SetEcoModeState write on a genuine transition. Wire format
is confirmed 0/1 (canonical doc correct); the G522 firmware rejects
no-op writes with device-specific NACK 0x0B.

BooleanValidator's prepare_write already contains the "skip if same as
current" branch — it just fires only when current_value is supplied,
which requires needs_current_value=True. For default-mask (0xFF)
validators, needs_current_value defaults to False so Setting.write
skips the pre-read and prepare_write gets current_value=None.

HeadsetEcoMode now builds its validator explicitly and forces
needs_current_value=True so Setting.write reads first, compares in
prepare_write, and skips redundant writes — matching LGHUB exactly.

Same fix may apply to other Centurion boolean features whose firmware
rejects no-op writes, but leaving those unchanged until observed.

lib/logitech_receiver/settings_templates.py

@@ -1591,6 +1591,24 @@ class HeadsetEcoMode(settings.Setting):
     feature = _F.HEADSET_BATTERY_SAVER
     validator_class = settings_validator.BooleanValidator
 
+    @classmethod
+    def build(cls, device):
+        # LGHUB's service layer for 0x0618 HeadsetBatterySaverMode compares
+        # incoming new_state against its cached current_state and SKIPS the
+        # devio SetEcoModeState write when they match (verified in
+        # on_headset_battery_saver_set_handler @ 0x100c21790). The G522
+        # firmware rejects no-op writes with device-specific NACK 0x0B.
+        #
+        # BooleanValidator's prepare_write already has the "skip if same as
+        # current" logic — it just needs needs_current_value=True to make
+        # Setting.write read the device state first. Default-mask (0xFF)
+        # BooleanValidators get needs_current_value=False, so we flip it here
+        # to match LGHUB's guard.
+        rw = settings.FeatureRW(cls.feature)
+        validator = settings_validator.BooleanValidator()
+        validator.needs_current_value = True
+        return cls(device, rw, validator)
+
 
 class HeadsetDoNotDisturb(settings.Setting):
     name = "headset-do-not-disturb"