refactor(transaction-pay-controller): consolidate origin gas payment resolution

[matthewwalsh0]

Explanation

Origin gas payment was decided independently inside each strategy. The Across, Relay and Server quote/submit modules each re-derived whether the origin gas fee could be paid from the source token, duplicating native-balance checks, gas-station eligibility probes and sponsorship predicates — and they did not always agree with one another.

• utils/gas-station.ts is replaced by utils/gas-payment.ts, which owns the whole decision: resolveGasStationCost for quote-time cost estimation, resolveGasPayment for submit-time payment-mode resolution, and shouldUseGasStation for the "is the gas station both needed and available" predicate.
• Every strategy module now delegates to those helpers, so the payment-mode priority (delegation > sponsored > gas fee token > native) and the sponsorship predicate are each expressed in exactly one place instead of being restated per strategy.
• The flows where a relayer covers origin gas instead of the user — the Relay execute flow and HyperLiquid withdrawals — are resolved through that same priority order via a single isDelegated input, rather than each carrying its own bespoke branch.
• The Relay single-transaction and batch submit paths are unified. These had diverged: the batch builder set gasFeeToken directly from the quote without consulting sponsorship, whereas the single-transaction path did consult it.

One reviewer-visible behaviour change falls out of that last point: a Relay batch request now omits gasFeeToken when gas is sponsored, matching what the single-transaction path already did. No existing test exercised the sponsored-plus-batch combination, so this is not covered by a test-diff.

Otherwise this is a pure refactor, covered by the existing suites passing unchanged. Nothing touched here is exported from the package index, so there is no consumer-facing change and no changelog entry.

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Medium Risk
Changes how origin gas is resolved and billed across all pay strategies at quote and submit time, including TransactionController options that affect what users are charged.

Overview
Introduces utils/gas-payment.ts in place of gas-station.ts, centralizing quote-time gas-station pricing (resolveGasStationCost), submit-time mode selection (resolveGasPayment), and post-submit verification (logGasPaymentOutcome). Across, Relay, and Server quote/submit paths now share one priority order: delegation → sponsored → source-token gas fee → native.

User-visible fix: when a quote prices origin gas in the source token, submit now always passes excludeNativeTokenForFee: true with gasFeeToken (Relay and Server previously omitted this, so TransactionController could drop the fee token at publish and charge native instead). Sponsored same-chain routes and relayer/HyperLiquid “no user origin gas” cases are handled through the same resolver rather than duplicated branches.

Relay batch submit now aligns with single-tx submit by suppressing gasFeeToken when gas is sponsored. gas-station.ts is removed; tests move to gas-payment.test.ts with expanded server/relay coverage.

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