Add battery_soc_full_hysteresis to work around inverters that clamp charge current at 100% SoC

[CossieRob]

Problem

Some inverters (reported on Fox and others) drop max charge current to 0A once the battery reaches 100% SoC, and won't accept charge current again until SoC has dropped a few percent (e.g. below 97%). Predbat isn't aware of this, so it can plan and command charging that the inverter silently won't deliver — wasting charge windows and producing an inaccurate forecast. The only current workaround is capping best_soc_max below 100%, which sacrifices usable capacity.

Closes #2513

Fix

Adds input_number.predbat_battery_soc_full_hysteresis (0–20%, default 0/off, expert mode). When set to match your inverter's behaviour (e.g. 3 for a 97% resume threshold), Predbat tracks whether the battery is within that band below 100% and, while so, both plans and live-controls as if charge current is unavailable — via a single shared choke point, find_charge_rate() in utils.py, used by the simulation, live control, and dashboard display.

State is tracked in PredBat.update_battery_full_hysteresis(), called each cycle, and persists across restarts as an attribute on the existing predbat.status sensor (same pattern as error_count).

C++ kernel

The fast prediction kernel (prediction_kernel.cpp) mirrors this with matching logic, and PK_PARITY_REVISION/KERNEL_PARITY_REVISION are bumped so any stale prebuilt binary falls back safely to the (correct) Python engine until CI rebuilds it.

Testing

• New tests in tests/test_battery_full_hysteresis.py: find_charge_rate clamp behaviour, the state machine (activate/hold/clear/no false-retrigger), restart persistence, and kernel-vs-Python parity for the hysteresis scenario.
• Full --quick suite passes (273/273, one pre-existing unrelated failure in test_enphase_api.py confirmed present on a clean main too).
• Rebuilt and ran kernel_parity (450+ randomized scenarios) and verify_kernel_binary.py against a locally compiled kernel — all bit-identical to the Python engine.
• black --check / flake8 show no new issues versus a clean checkout.

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