feat(plan): show when live solar may charge the battery

[frahlg]

Problem

Refs #1482.

Core already lets live solar beyond the plan charge the battery when the plan buys grid energy later at an import price above this slot's export price plus the minimum spread (livePVSurplusSoCCap → SlotDirective.LivePVSurplusSoCCap → pvSurplusAbsorbCap in dispatch). Without that permission, an idle or charging arbitrage slot sends surprise sun to the grid.

A beta tester saw exactly that (battery idle at 38 %, 3.5 kW to the grid, plan active) and could not tell from the UI why. The plan API did not expose the permission, so the Plan card could not say whether extra sun will be stored or sold.

Change

• mpc.Action gains live_pv_surplus_soc_cap (0–1 SoC). Core computes it once when it publishes a plan, on every path: replan (every solver and the fallback), InstallPlan, and restore from a diagnostic. The DP shadow copies the plan, so it keeps the values.
• SlotDirectiveAt reads the stored value instead of recomputing it, so the API shows the number dispatch uses.
• The field is always sent, also when zero, so a client can tell "no permission" from a box that predates the field.
• No change to dispatch rules or to which slots get permission. dispatch.go is untouched (open PRs feat(control): show command limits and measured response tiers #1474 and fix(control): mitigate PV-only export over limits #888 change it).

Verification

• New: TestReplanStoresLivePVSurplusSoCCap (external optimizer, Core planner, Core fallback after an optimizer failure), TestReplanWithoutLaterGridChargeSendsZeroLivePVSurplusSoCCap, a restore test, and TestMPCPlanCarriesLivePVSurplusSoCCap (the /api/mpc/plan value equals the directive value for the same slot).
• TestSlotDirectiveAt now publishes through InstallPlan, with the same assertions.
• make verify passed on this commit.

#1486 is the Plan card change that reads the field. Either can merge first: the card says nothing about extra sun unless the plan carries the field.

🤖 Generated with Claude Code

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Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-01T14:42:43.528742Z	d316cc1	PR opened

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