bug(ack-pay): paymentRequest.serviceCallback rejects DID URIs despite docs and sibling fields

[kutluhaneth46]

Summary

PaymentRequest.serviceCallback is documented as a URL or DID URI, and sibling fields paymentService / receiptService already use a shared urlOrDidUri schema. serviceCallback is still URL-only in both Valibot and Zod, so a DID callback fails schema parse / signed request creation.

Affected files

• packages/ack-pay/src/schemas/valibot.ts
• packages/ack-pay/src/schemas/zod.ts
• docs/ack-pay/payment-request-payload.mdx (documents URL or DID URI)

Expected

A serviceCallback like did:web:merchant.example should parse the same way paymentService / receiptService do.

Actual

v.url() / z.url() reject DID URIs.

Proposed fix

Reuse urlOrDidUri for serviceCallback in both schema venues and add parity tests.

AI usage disclosure

Drafted with Cursor assistance; I reviewed the schema/docs mismatch and will own the fix.