[codex] retry compressed requests uncompressed

[rphilizaire-openai]

Summary

• Retry an HTTP Responses request exactly once without compression when a compressed HTTP 400 carries x-openai-retry-uncompressed: true.
• Require the original request to use zstd and the response signal to be exactly true; generic 400s remain terminal.
• Rebuild the request with Compression::None while preserving existing authentication and inference-attempt telemetry.

Paired server signal: https://github.com/openai/openai/pull/1087044

Validation

• cargo check -p codex-core --lib
• Existing request-compression tests (2 passed)
• cargo clippy -p codex-core --lib --no-deps -- -D warnings
• just fmt