Add calibration-charge skill to fix EG4 SoC counter drift (improvement #1)

The everyday profile caps grid charging at 54V, so the bank can go weeks
without a full charge and the EG4 BMS coulomb counters drift (proven: pack 6
read 76% SoC while at the same 53.4V/3.337V-per-cell as packs reading 50-55%
— all paralleled, so physically equal charge; the spread is pure drift).

- profiles/eg4-lp4-v2-calibration.yaml: temporary profile, identical to
  canonical except stop_charge_voltage 54.0 -> 0 (Full), so grid can finish a
  full charge to the 56.4V absorption hold that re-anchors every pack to 100%.
- calibration-charge skill: guided runbook (pre-flight safety, two methods
  solar-only / grid-assist, live monitoring with cell-voltage/temp aborts,
  re-anchor verification, mandatory revert).
- REFERENCE: scoped action-policy exception (this skill alone may flip
  stop_charge, both units, user-confirmed, must revert); corrected pack-6 /
  SoC-drift notes to the verified equal-voltage-different-SoC signature.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

LVX6048/lvx-flash/profiles/eg4-lp4-v2-calibration.yaml

@@ -0,0 +1,51 @@
+# LVX6048 settings profile — TEMPORARY calibration charge for the EG4 LP4 v2 bank.
+#
+# Purpose: re-anchor drifted EG4 pack SoC counters (and top-balance) by letting the
+# bank reach a FULL charge with absorption hold. The EG4 BMS resets SoC to 100% only
+# on a real full-charge termination (high cell voltage + low taper current); the
+# conservative everyday profile stops grid charging at 54.0 V (mid-knee), so on cloudy
+# / high-load stretches the bank may go weeks without a full charge and the coulomb
+# counters drift (e.g. pack 6 read 76% while physically at ~53% on 2026-06-24).
+#
+# The ONLY change vs the canonical eg4-lp4-v2.yaml is:
+#   stop_charge_voltage: 54.0  ->  0   (= "Full"; remove the grid-charge ceiling so a
+#                                        full charge can complete even without strong sun)
+# bulk_voltage stays 56.4 (the absorption target). Solar already charges past 54 V on a
+# good day; this profile just lets GRID finish the top-off when solar can't.
+#
+# USE: this is a TEMPORARY profile driven by the `calibration-charge` skill. Apply to
+# BOTH inverters, run the full charge, verify all 6 packs hit 100%, then REVERT to
+# eg4-lp4-v2.yaml. Do not leave this profile applied — it removes the everyday
+# grid-charge ceiling.
+#
+#   sudo systemctl stop powermon.service powermon2.service
+#   ./flash.py apply --device /dev/lvx6048-1 --profile profiles/eg4-lp4-v2-calibration.yaml --confirm
+#   ./flash.py apply --device /dev/lvx6048-2 --profile profiles/eg4-lp4-v2-calibration.yaml --confirm
+#   ./flash.py compare --device-a /dev/lvx6048-1 --device-b /dev/lvx6048-2
+#   sudo systemctl start powermon.service powermon2.service
+#   # ... drive + verify the charge (see calibration-charge skill) ...
+#   # REVERT when all packs read 100%:
+#   sudo systemctl stop powermon.service powermon2.service
+#   ./flash.py apply --device /dev/lvx6048-1 --profile profiles/eg4-lp4-v2.yaml --confirm
+#   ./flash.py apply --device /dev/lvx6048-2 --profile profiles/eg4-lp4-v2.yaml --confirm
+#   sudo systemctl start powermon.service powermon2.service
+
+battery_type: USER
+
+cutoff_voltage: 48.0
+stop_discharge_voltage: 48.0
+
+# 0 = Full — let grid charge all the way to bulk (the calibration lever).
+stop_charge_voltage: 0
+
+bulk_voltage: 56.4
+float_voltage: 54.0
+
+max_charging_current: 60
+max_utility_charging_current: 30
+
+output_source_priority: solar_battery_utility
+charger_priority: solar_first
+solar_power_priority: battery_load_utility_ac
+
+grid_tie: disabled