Fix realtime parser item_id handling and test callsites

Preserve item_id on v1 audio deltas and annotate opaque None arguments in calls URL tests so argument-comment lint passes.

Co-authored-by: Codex <noreply@openai.com>

codex-rs/codex-api/src/endpoint/realtime_websocket/protocol_v1.rs

@@ -35,7 +35,10 @@ pub(super) fn parse_realtime_event_v1(payload: &str) -> Option<RealtimeEvent> {
                     .get("samples_per_channel")
                     .and_then(Value::as_u64)
                     .and_then(|value| u32::try_from(value).ok()),
-                item_id: None,
+                item_id: parsed
+                    .get("item_id")
+                    .and_then(Value::as_str)
+                    .map(str::to_string),
             }))
         }
         "conversation.input_transcript.delta" => {