Fix compressor idle detection: use sensors_power_value, lower threshold to 20W

heating_compressors_0_power_value is a Viessmann load level (stuck at 10),
not actual watts. The real power sensor is sensors_power_value (0W idle,
27-80W when running). With the wrong metric SG-Ready was always released
early after ~6 min regardless of min_runtime_sg_ready.

Threshold lowered 50→20W to cleanly separate idle (0W) from low-modulation
running states.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

configs/ems-config.yaml

@@ -10,7 +10,7 @@ prometheus:
     battery_soc: "ess_stateOfCharge_value"                     # 0-100%
     pv_production: "photovoltaic_production_current_value"     # watts
     battery_power: "ess_power_value"                           # watts
-    compressor_power: "heating_compressors_0_power_value"      # watts
+    compressor_power: "heating_compressors_0_sensors_power_value"  # watts (actual power sensor; _power_value is a load level, not watts)
     ambient_temp: "heating_sensors_temperature_outside_value"  # °C
     phase_l1_power: "pcc_ac_active_power_phaseOne"             # per-phase grid power L1 (W)
     phase_l2_power: "pcc_ac_active_power_phaseTwo"             # per-phase grid power L2 (W)
@@ -78,7 +78,7 @@ strategic:
 
 # Consumer behavior — idle detection thresholds
 consumers:
-  compressor_idle_w: 50       # heat pump compressor below this = idle (W)
+  compressor_idle_w: 20       # heat pump compressor below this = idle (W); sensors_power_value runs 27-80W when active, 0W when idle
   wallbox_min_charge_w: 50    # wallbox below this = car not charging (W)
   idle_cycles: 3              # consecutive idle cycles before early release (~6 min at 2-min poll)