fix: preserve fee token in fee payer signing

[brendanjryan]

Summary

• Preserve the configured chain fee token when the fee payer handler co-signs sponsored transactions
• Add regression coverage for raw transaction sponsorship output
• Add a patch changeset

mppx impact

mppx pull mode submits a user-signed sponsored Tempo transaction to the hosted fee payer. Sponsored sender signatures intentionally omit feeToken, so the fee payer must choose and include the fee token when it co-signs. The handler was deserializing the raw transaction and signing it without restoring client.chain.feeToken, producing a final sponsored envelope with a fee payer signature but no fee token. That causes mppx settlement/broadcast to fail during Tempo fee validation because the fee token path is missing or wrong.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/tempoxyz/tempo-ts/tempo.ts@184

commit: 33251f4

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve explicit null fee token settings

When the fee payer client is configured with chain.extend({ feeToken: null }) to opt into protocol-selected fee tokens, this truthiness guard treats that explicit setting as absent. In that scenario, if the deserialized user transaction already contains a concrete feeToken, the earlier ...transaction spread keeps that token and the fee payer signs using it instead of preserving the configured null preference.

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[brendanjryan]

pulling this into accounts SDK re: archive notice