Require hard per-cell provider cap and normalized termination receipt

[myobie]

Problem

The preregistered vrs-catalog-activation-present / vrs-catalog-activation-absent provider pair is held because the current provider launch path cannot guarantee both of these properties:

1. a hard USD 0.05 cap enforced before and during each cell; and
2. exactly one normalized usage/cost receipt available after every provider termination, including product failure and watchdog timeout.

Source-level command assertions are insufficient. If a provider process is externally terminated before its usage data is durably emitted, the runner cannot safely distinguish a product timeout from an infrastructure/accounting failure.

This is the external capability blocking the paid half of draft PR #60. The PR's model-free A–D proof and living-spec judge remain frozen; no paid result is inferred.

Required adapter contract

Before launch, the selected provider path must prove a real hard ceiling of USD 0.05 for the complete cell.

After termination, it must emit exactly one normalized receipt bound to:

• schema version;
• exact cell;
• provider and model;
• non-negative integer input/output token counts;
• actual cost_usd;
• exact budget_usd: 0.05; and
• termination status: pass, fail, timeout, or error.

The runner must durably persist the receipt before verdict classification.

Acceptance

The existing public model-free boundary harness in PR #60 must remain green:

• product FAIL plus valid under-budget receipt persists, then paired control runs;
• watchdog timeout plus valid under-budget timeout receipt persists, then paired control runs;
• missing or malformed receipt writes STOPPED before control; and
• valid over-budget receipt persists, then writes STOPPED before control.

A real adapter acceptance must additionally prove that its cap is enforced by the provider path and that timeout teardown cannot race or erase the receipt. Provider-specific work belongs to the owning adapter/runtime repository; this evals issue owns the cross-repo acceptance dependency and unblock criteria.

Guardrails

• Do not weaken the VRS living-spec judge.
• Do not alter the frozen matched inputs to manufacture a result.
• Do not infer authorization for a provider run from this issue.
• Keep the pair held until an exact owner-reviewed adapter source and immutable capability receipt are linked here.