Add SOCKS5 TCP MITM coverage

[winston-openai]

Summary

• reuse the MITM HTTPS serving path for raw SOCKS5 TCP streams
• route limited-mode and hooked SOCKS5 TCP requests through MITM before dialing upstream
• keep SOCKS5 UDP limited-mode behavior unchanged

Validation

• just fmt
• cargo test -p codex-network-proxy
• just fix -p codex-network-proxy
• git diff --check

[github-actions]

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