Parent Issue

Part of #315 (TCP receive std::span callback migration)

Summary

Update messaging components that directly use internal::tcp_socket to consume the new std::span<const uint8_t> receive callback internally, removing one copy/allocation per read while keeping existing public APIs intact.

Background

Today the receive path for messaging over TCP typically looks like:

1. tcp_socket::do_read() allocates + copies into std::vector<uint8_t>
2. messaging_session / messaging_client then copies that vector again (e.g., enqueueing)

After #316, step (1) can become span-view based (no vector allocation).

Proposed Solution

1) messaging_session

• Register tcp_socket with set_receive_callback_view(...)
• Change internal messaging_session::on_receive(...) to accept std::span<const uint8_t>
• When queueing/retaining data is required, copy from span into a single std::vector<uint8_t> once

Files:

• src/session/messaging_session.cpp
• include/kcenon/network/session/messaging_session.h

2) messaging_client

• Register tcp_socket with set_receive_callback_view(...)
• Change internal messaging_client::on_receive(...) to accept std::span<const uint8_t>
• Keep existing external set_receive_callback(std::function<void(const std::vector<uint8_t>&)>) working by copying span into a vector only at the API boundary

Files:

• src/core/messaging_client.cpp
• include/kcenon/network/core/messaging_client.h

Acceptance Criteria

• messaging_session uses tcp_socket span callback and performs at most one copy when it must retain data
• messaging_client uses tcp_socket span callback and keeps public vector-based callback behavior unchanged
• Removes one allocation/copy per read vs current baseline in the messaging path
• Unit/integration tests pass

Test Plan

• Run:
  • ctest --output-on-failure -R messaging
  • ctest --output-on-failure (full suite as time permits)