Trace turn context creation and realtime state checks (#40017)

## What changed

- Add trace-level `turn_context.make` instrumentation around turn context
  construction.
- Add a trace-level `realtime_conversation.running_state` span around realtime
  conversation state checks.
- Skip recording function arguments in both spans.

GitOrigin-RevId: f0b905e75eb487432f56a2efdd65972f5322555d

codex-rs/core/src/realtime_conversation.rs

@@ -503,6 +503,11 @@ impl RealtimeConversationManager {
         self.mode_instructions.lock().await.clone()
     }
 
+    #[tracing::instrument(
+        name = "realtime_conversation.running_state",
+        level = "trace",
+        skip_all
+    )]
     pub(crate) async fn running_state(&self) -> Option<()> {
         let state = self.state.lock().await;
         state

codex-rs/core/src/session/turn_context.rs

@@ -616,6 +616,7 @@ impl Session {
     }
 
     #[allow(clippy::too_many_arguments)]
+    #[instrument(name = "turn_context.make", level = "trace", skip_all)]
     pub(crate) fn make_turn_context(
         thread_id: ThreadId,
         session_id: SessionId,