Gas payment refactor

[wilfreddenton]

Note

High Risk
High risk because it refactors gas metering/payment accounting across execution, introduces a new sponsorship mode for BLS aggregates, and changes the DB schema/results API to track payers, all of which affect consensus-critical execution and billing.

Overview
Refactors gas handling so Publish/Call ops carry an explicit Payment (payer signer_id + gas_limit) derived from a signed PaymentIntent on each Inst, replacing the prior direct gas_limit field and removing runtime-global set_gas_limit usage.

Adds BLS-aggregate sponsorship: AggregateInfo now includes optional publisher_sponsorship (validated non-zero), and aggregate ops can declare PaymentIntent::Sponsored which resolves to publisher-paid gas via a per-bulk PublisherOffer; direct (non-aggregate) Sponsored intents are rejected.

Persists and exposes gas payer attribution by adding payer_signer_id to contract_results (schema + queries + TS bindings) and wiring runtime hold/release + result insertion to charge/release tokens against the resolved payer. Updates API/test/macro code paths to pass payment through Runtime::execute/publish, adds execute_api for core-paid native API wrappers, and introduces a new regtest e2e test verifying publisher-paid sponsored ops.

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