feat: add agent roles to collab tools (#9275)

Add `agent_type` parameter to the collab tool `spawn_agent` that
contains a preset to apply on the config when spawning this agent

codex-rs/core/src/tools/spec.rs

@@ -1,3 +1,4 @@
+use crate::agent::AgentRole;
 use crate::client_common::tools::ResponsesApiTool;
 use crate::client_common::tools::ToolSpec;
 use crate::features::Feature;
@@ -441,6 +442,15 @@ fn create_spawn_agent_tool() -> ToolSpec {
             description: Some("Initial message to send to the new agent.".to_string()),
         },
     );
+    properties.insert(
+        "agent_type".to_string(),
+        JsonSchema::String {
+            description: Some(format!(
+                "Optional agent type to spawn ({}).",
+                AgentRole::enum_values().join(", ")
+            )),
+        },
+    );
 
     ToolSpec::Function(ResponsesApiTool {
         name: "spawn_agent".to_string(),