chore: enable await-holding clippy lints

Follow-up to https://github.com/openai/codex/pull/18178, where we said the await-holding clippy rule would be enabled separately.

Enable `await_holding_lock` and `await_holding_invalid_type` after the preceding commits fixed or explicitly documented the current offenders.

codex-rs/Cargo.toml

@@ -380,6 +380,8 @@ zeroize = "1.8.2"
 rust = {}
 
 [workspace.lints.clippy]
+await_holding_invalid_type = "deny"
+await_holding_lock = "deny"
 expect_used = "deny"
 identity_op = "deny"
 manual_clamp = "deny"

codex-rs/login/src/auth/auth_tests.rs

@@ -243,6 +243,7 @@ fn dummy_chatgpt_auth_does_not_create_cwd_auth_json_when_identity_is_set() {
         agent_runtime_id: "agent_123".to_string(),
         agent_private_key: "pkcs8-base64".to_string(),
         registered_at: "2026-04-13T12:00:00Z".to_string(),
+        background_task_id: None,
     };
 
     auth.set_agent_identity(record.clone())