[chris7iu]

Summary

• Adds opt-in gzip request body compression for outbound Codex HTTP POST requests (codex.requestCompression in ~/.config/claude-code-proxy/config.json or CCP_CODEX_REQUEST_COMPRESSION=1).
• When codex.requestCompression is enabled and no explicit codex.transport / CCP_CODEX_TRANSPORT is set, defaults codex_transport() to Http so requests use gzip-compressed HTTP POST (Content-Encoding: gzip) instead of uncompressed WebSocket text frames.
• Preserves readable JSON payloads in 020-upstream-request.json traffic capture while recording compressedBytes in 021-upstream-request-metadata.json.
• Reduces outbound Codex request payload bytes by ~80-88% on large multi-turn / tool-heavy conversations, significantly cutting metered proxy/egress bandwidth.

Test Plan

• cargo fmt --check
• cargo clippy --all-targets -- -D warnings
• cargo test --lib config::tests::codex_request_compression
• cargo test --lib providers::codex::client::tests::http_request_compression
• Verified live against https://chatgpt.com/backend-api/codex/responses (HTTP/2 200, event: response.created).