## Summary
- parse chatgpt_account_is_fedramp from signed ChatGPT auth metadata
- add _account_is_fedramp=true to ChatGPT backend-api requests only for
FedRAMP ChatGPT-auth accounts
## Summary
- Move auth header construction into the
`AuthProvider::add_auth_headers` contract.
- Inline `CoreAuthProvider` header mutation in its provider impl and
remove the shared header-map helper.
- Update HTTP, websocket, file upload, sideband websocket, and test auth
callsites to use the provider method.
- Add direct coverage for `CoreAuthProvider` auth header mutation.
## Testing
- `just fmt`
- `cargo test -p codex-api`
- `cargo test -p codex-core
client::tests::auth_request_telemetry_context_tracks_attached_auth_and_retry_phase`
- `cargo test -p codex-core` failed on unrelated/reproducible
`tools::handlers::multi_agents::tests::multi_agent_v2_followup_task_interrupts_busy_child_without_losing_message`
---------
Co-authored-by: Celia Chen <celia@openai.com>
