fix(levelcode): report account activity spend at RETAIL, not raw wire cost

[ndemianc]

The account page has been showing two different units for the same quantity: a retail-converted balance (1,279 credits left) above, and per-day / per-model spend summed straight from usage_events.cost_micros below.

The ledger stores what a request cost us at the wire. So those rows understated what the customer actually spent — by the margin — and could not be reconciled against the credits the same page reported as spent.

This is a real bug independent of credits: the per-model "cost" on the account page has been understating user spend in dollars all along.

What changed

Activity.for_user takes an optional plan_key and converts the aggregates through retail_micros — one rounding per figure, rather than one per ledger row. The account controller passes the caller's plan.

Left opt-in rather than baked into the aggregation, deliberately: this is a shared service, and an operator-side caller wants real COGS, not what the customer was charged. Passing no plan_key still yields raw cost.

Why the admin panel is not converted

Its figures carry no retail conversion — they are real COGS, what we pay providers. Credits are a retail unit (≈2× cost via CREDIT_COGS_RATIO), so rendering them there would conflate what we pay with what the customer is charged, and destroy the one view where margin is legible. Dollars are correct there.

Verification

971 examples, 0 failures. New specs assert the retail figure on the per-model row, the per-day total and the per-day model rows — with a precondition that retail actually exceeds cost, so the assertion cannot pass vacuously. One more pins that the no-plan_key path still returns raw cost.

Deploy order

The matching frontend change (onetime #88) renders these figures as credits. Ship this first — until it lands, that UI would divide raw cost and understate spend by the margin.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Fixes a unit mismatch on the Levelcode account activity endpoint by reporting customer-facing spend in the same retail denomination as the displayed balance, while preserving an opt-in path for operator/internal callers to retrieve raw COGS.

Changes:

• Add optional plan_key: to Levelcode::Activity.for_user to convert aggregated cost_micros values via Levelcode.retail_micros when provided.
• Pass current_plan_key from the account activity controller action so the account page receives retail-denominated spend.
• Add request specs asserting retail conversion for per-model + per-day figures, and that omitting plan_key preserves raw cost.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
spec/requests/api/levelcode/v1/account_spec.rb	Adds coverage for retail spend reporting and the opt-in raw-cost behavior.
app/services/levelcode/activity.rb	Introduces plan_key: and applies retail conversion to aggregated cost figures when present.
app/controllers/api/levelcode/v1/account_controller.rb	Passes the current plan key into Activity.for_user for retail reporting on the account activity endpoint.

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