feat: submit decision-flow NFS-e through dedicated endpoint

[vitormattos]

Advances #56.

Summary

• add NfseClientInterface::emitDecision() as an opt-in first-class operation
• build the complete NFS-e with the existing DecisionNfseBuilder
• sign the complete NFS-e through the existing XMLDSig signer boundary
• submit exactly one mutable request to POST /decisao-judicial/nfse
• encode the signed XML as GZip+Base64 under the official xmlGZipB64 JSON field
• reuse the normal authorized NFS-e response parser so query/cancel remain the ordinary APIs after authorization
• add a fake-transport protocol contract test proving endpoint, method and payload shape

Protocol source

Current production manual documents POST /decisao-judicial/nfse; the production API contract defines NFSeBypassPostRequest.xmlGZipB64.

Safety

• no retry is added around the mutable POST
• normal emit(DpsData) remains unchanged
• legal eligibility is not inferred

DCO/signing

Commit created by the configured Git signing MCP with cryptographic verification and DCO.