feat: list agents for sub-agent v2 (#15621)

Add a `list_agents` for multi-agent v2, optionally path based

This return the task and status of each agent in the matched path

codex-rs/core/src/state/turn.rs

@@ -198,6 +198,10 @@ impl TurnState {
         }
     }
 
+    pub(crate) fn pending_input_snapshot(&self) -> Vec<ResponseInputItem> {
+        self.pending_input.clone()
+    }
+
     pub(crate) fn has_pending_input(&self) -> bool {
         !self.pending_input.is_empty()
     }