Deprecate legacy OPP envelope metadata

[huangminghuang]

Summary

• remove legacy outbound envelope table fields from sysio.msgch ABI/types
• keep protobuf legacy envelope fields documented as deprecated while omitting them from WIRE DataStream serialization
• update outbound envelope ABI shape to rely on raw_envelope/envelope_hash instead of inline Merkle/message-id metadata

Verification

• regenerated OPP attestation protobuf outputs to fix stale generated CDT headers
• ninja -C /home/ssm-user/code/wire/wire-sysio/build/debug/contracts sysio.msgch
• recreated and ran local OPP cluster from /home/ssm-user/code/wire/.clusters/opp-legacy-envelope
• verified sysio.msgch::outenvelopes rows no longer expose merkle_root, start_message_id, or end_message_id
• decoded emitted OPP debugging envelopes and confirmed legacy protobuf fields remain zero-length

Notes

• Full cmake --build build/debug -j2 reached late native dispatch generation but failed in unrelated sysio.opreg_native dispatch code with missing sysio::opreg::stake; cluster-critical WIRE binaries/contracts and sysio.msgch rebuilt and deployed successfully.