fix(car-charging): don't let an empty exclusive plan block later cars

[chalfontchubby]

Summary

Reported in #4305 - a shared-charger, 2-car setup (both car profiles pointed at the same Zappi's status sensor) showed zero Car kWh for an actively-charging session, despite every individual signal (plugged in, dispatch active, real session energy accumulating, genuine SoC/limit gap) confirming the car really was charging and really did need more.

Root cause, confirmed against the reporter's own debug.yaml: in a shared-charger setup, car_charging_planned/car_charging_now can read true for every car profile sharing the same physical sensor, not just the one actually plugged in. fetch_sensor_data_car_planning()'s exclusive-charging break (fetch.py:1141) fired on car_charging_planned[car_n] and car_charging_exclusive[car_n] alone - so car 0 (not actually plugged in, but reading planned=True off the shared sensor) hit the break and stopped the loop before car 1 (the car genuinely charging) was ever considered. Car 0's own charging need happened to be zero (SoC already at its own limit), so plan_car_charging() correctly returned nothing for it - but the loop still treated it as "the" exclusive session and bailed out, silently eating car 1's turn. car_charging_slots ended up [[], []].

Fix: only let the exclusive break fire once a car has actually produced a non-empty plan:

if self.car_charging_planned[car_n] and self.car_charging_exclusive[car_n] and self.car_charging_slots[car_n]:
    self.log("Car {} charging is exclusive, will not plan other cars".format(car_n))
    break

Behaviour is unchanged for the normal case (a car with a genuine charging need and exclusive=True still breaks immediately, same as before) - the only change is that a car with planned=True but an empty resulting plan no longer blocks later cars from getting their turn.

(A fix based on checking a car_charging_plugged_in entity was considered first, but that concept doesn't actually exist anywhere in Predbat's config today - would have meant introducing a whole new per-car entity rather than using data already computed a few lines above.)

Test plan

• New regression test run_multi_car_shared_charger_exclusive_test in test_multi_car_iog.py, modelled on the setup from the reporter's debug.yaml (car 0: planned=True, exclusive=True, SoC already at its own limit; car 1: genuine SoC/limit gap) - asserts car 1 still gets planned
• Verified the new test actually fails without the fix (reverted fetch.py locally, confirmed the test catches it, then restored)
• ./run_all --test multi_car_iog - all pass
• pre-commit (ruff, black, cspell) run against the changed files, passed

Fixes #4305

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR fixes a multi-car shared-charger edge case where an “exclusive charging” early-exit in fetch_sensor_data_car_planning() could prevent later car profiles from being planned when an earlier car reports planned=True via a shared sensor but produces an empty plan (e.g., already at its limit). It also adds a regression test based on the reported scenario in #4305.

Changes:

• Refines the exclusive-charging break condition in fetch_sensor_data_car_planning() to only trigger once an actual non-empty charging plan exists.
• Adds a regression test to ensure a later car still gets planned in shared-sensor + exclusive setups.
• Registers the new regression test in the multi-car IOG test suite.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
apps/predbat/fetch.py	Adjusts exclusive-charging loop break logic during car planning to avoid skipping later cars when the current car produced no plan.
apps/predbat/tests/test_multi_car_iog.py	Adds and wires a regression test for the shared-charger exclusive-planning scenario from issue #4305.