Include spawn agent model metadata in app-server items (#14410)

- add model and reasoning effort to app-server collab spawn items and
notifications
- regenerate app-server protocol schemas for the new fields

---------

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

codex-rs/protocol/src/protocol.rs

@@ -3179,6 +3179,10 @@ pub struct CollabAgentSpawnEndEvent {
     /// Initial prompt sent to the agent. Can be empty to prevent CoT leaking at the
     /// beginning.
     pub prompt: String,
+    /// Model requested for the spawned agent.
+    pub model: String,
+    /// Reasoning effort requested for the spawned agent.
+    pub reasoning_effort: ReasoningEffortConfig,
     /// Last known status of the new agent reported to the sender agent.
     pub status: AgentStatus,
 }