Capture sender context for codex_app.create_thread deliveries (#54590)

## What changed

Recognize `codex_app.create_thread` deliveries when capturing sender context so Guardian receives the sender's recent user messages and assistant context for delegated tasks.

## Testing

Extend the sender-context integration test to cover `create_thread`, including reviewer-only context and clearing the snapshot on a subsequent delivery without sender provenance.

GitOrigin-RevId: 7a47c3ac5b9c9405e6728010c494529274b7b73d

codex-rs/core/src/agent/control/sender_context.rs

@@ -38,6 +38,7 @@ impl LocalAgentRuntime {
         if !matches!(
             (namespace.as_str(), name.as_str()),
             ("codex_app" | "codex_tui", "send_message_to_thread")
+                | ("codex_app", "create_thread")
                 | ("cloud_threads", "send_message")
         ) {
             return None;