feat(plan): split the Import p cell when the car's own rate diverges

[chalfontchubby]

Summary

• On Octopus Intelligent Go, a car's own low-rate dispatch allowance is capped independently of the house rate - once used up, the car falls back to the peak rate while the house keeps its real (possibly still cheap) rate for the same clock-time. The plan previously only ever showed the house rate, with no way to see the car was actually paying more for the same slot.
• Adds car_charge_slot_rate() (kWh-weighted average rate across any car charging windows active in a slot) and splits the Import p cell - house on the left, car on the right, each independently coloured and with its own hover tooltip - whenever the two diverge by more than 0.01. Server HTML and the client-side JS renderer are both updated; editable/override mode is left untouched since overrides apply to the single household rate.
• Fixes Plan doesn't show the car's own rate once its IOG dispatch cap is exhausted #4646.

Relationship to #4644

Independent of #4644 (the IOG daily-cap slot-splitting fix) - verified no file/line overlap and no shared commit history, so either can merge first or standalone. This one just displays whatever rate is already present in car_charging_slots, regardless of which version of that calculation produced it.

Test plan

• ./run_all --quick passes
• New test in test_plan_json_rate_adjust.py covers both the JSON fields (car_rate, rate_split, car_rate_color) and the rendered split-cell HTML with both tooltips
• run_pre_commit clean
• Also fixed a pre-existing test-isolation bug found along the way: run_load_octopus_slots_tests() never set num_cars itself, silently depending on whatever a prior test in the same run left it as

🤖 Generated with Claude Code

[Copilot]

🟡 Changes recommended

Unresolved HTML escaping, misleading tooltip, and historical rate fallback issues remain.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds separate household and car import-rate display when charging rates diverge.

Changes:

• Calculates weighted car charging rates and adds related JSON fields.
• Splits server/client Import cells with separate tooltips.
• Adds regression coverage and fixes test isolation.

File summaries

File	Review summary
apps/predbat/web_helper.py	Moderate: avoid implying an IOG cap whenever rates merely differ.
apps/predbat/tests/test_plan_json_rate_adjust.py	Adds coverage for divergent rates and split rendering.
apps/predbat/tests/test_octopus_slots.py	Makes car-count setup explicit for test isolation.
apps/predbat/plan.py	Moderate: historical reconstructed slots need a household-rate fallback instead of zero.
apps/predbat/output.py	Critical: escape user-configurable tooltip content; moderate: avoid misleading cap wording.

Review details

Suppressed comments (2)

apps/predbat/tests/test_plan_json_rate_adjust.py:150

• With the default plan_interval_minutes of 30, minutes_now is only aligned to 5 minutes, while publish_html_plan() emits slot_minute values aligned to 30. Unless the test runs exactly on a half-hour, this lookup returns None, prints only a warning, and skips all the new assertions, so the test can pass without covering the feature. Align car_minute to the plan interval (or select the row containing it) and fail if the row is missing.

    car_minute = my_predbat.minutes_now
    my_predbat.car_charging_slots[0] = [{"start": car_minute, "end": car_minute + 30, "kwh": 3.0, "average": 28.0, "cost": 84.0, "soc": 0.0, "octopus": True}]

    html_plan, raw_plan = my_predbat.publish_html_plan(pv_step, pv_step, load_step, load_step, my_predbat.end_record, publish=False)
    car_row = next((row for row in raw_plan["rows"] if row.get("slot_minute") == car_minute), None)

apps/predbat/web_helper.py:6533

• The added test checks the server-generated html_plan, but it never validates this read-only renderPlanTable() branch. A mismatch in the new rate_split/car_rate fields or a client-side toFixed() failure would therefore pass the test suite while the History/Baseline renderer is broken. Add a renderer-level assertion or browser test for both a split row and a non-split row.

                } else if (row.rate_split) {
                    // Car's own rate has diverged from the house rate (IOG dispatch cap reached) -
                    // split the cell, house on the left, car on the right, each with its own tooltip.
                    const houseTitle = escapeAttr(`House rate: ${row.import_rate.toFixed(2)}${currencyMinor}/kWh`);
                    const carTitle = escapeAttr(`Car rate: ${row.car_rate.toFixed(2)}${currencyMinor}/kWh (IOG dispatch cap reached)`);

• Files reviewed: 5/5 changed files
• Comments generated: 4
• Review effort level: Lite

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[chalfontchubby]

Addressed in efb0e35:

• HTML-escaped the split cell's title attributes (currency_symbols is user-configurable text; unescaped it could break out of the attribute server-side, the client JS path already escaped it).
• Reworded the car tooltip to "differs from house rate" instead of asserting "IOG dispatch cap reached" - any diverging car window average triggers the split, not only an IOG cap.
• car_charge_slot_rate() now skips windows with no average key (non-Octopus historical reconstruction in the Yesterday view) instead of treating them as 0p/kWh, which was falsely flagging ordinary charging as a rate divergence.