fix(codex): normalize request session header to `Session-Id` and preload codex headers

- Replaced legacy `Session_id` usage with canonical `Session-Id` when propagating cache/session state.
- Added ensured request headers for `X-Codex-Window-Id`, `Thread-Id`, `Session-Id`, and `X-Openai-Internal-Codex-Responses-Lite`.
- Removed macOS-only `Session_id` auto-generation fallback path for request header setup.