fix(subagents) share execpolicy by default (#13702)

## Summary
If a subagent requests approval, and the user persists that approval to
the execpolicy, it should (by default) propagate. We'll need to rethink
this a bit in light of coming Permissions changes, though I think this
is closer to the end state that we'd want, which is that execpolicy
changes to one permissions profile should be synced across threads.

## Testing
- [x] Added integration test

---------

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

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

@@ -107,6 +107,9 @@ impl AgentControl {
         let inherited_shell_snapshot = self
             .inherited_shell_snapshot_for_source(&state, session_source.as_ref())
             .await;
+        let inherited_exec_policy = self
+            .inherited_exec_policy_for_source(&state, session_source.as_ref(), &config)
+            .await;
         let session_source = match session_source {
             Some(SessionSource::SubAgent(SubAgentSource::ThreadSpawn {
                 parent_thread_id,
@@ -189,6 +192,7 @@ impl AgentControl {
                             session_source,
                             /*persist_extended_history*/ false,
                             inherited_shell_snapshot,
+                            inherited_exec_policy,
                         )
                         .await?
                 } else {
@@ -200,6 +204,7 @@ impl AgentControl {
                             /*persist_extended_history*/ false,
                             /*metrics_service_name*/ None,
                             inherited_shell_snapshot,
+                            inherited_exec_policy,
                         )
                         .await?
                 }
@@ -271,6 +276,9 @@ impl AgentControl {
         let inherited_shell_snapshot = self
             .inherited_shell_snapshot_for_source(&state, Some(&session_source))
             .await;
+        let inherited_exec_policy = self
+            .inherited_exec_policy_for_source(&state, Some(&session_source), &config)
+            .await;
         let rollout_path =
             find_thread_path_by_id_str(config.codex_home.as_path(), &thread_id.to_string())
                 .await?
@@ -283,6 +291,7 @@ impl AgentControl {
                 self.clone(),
                 session_source,
                 inherited_shell_snapshot,
+                inherited_exec_policy,
             )
             .await?;
         reservation.commit(resumed_thread.thread_id);
@@ -499,6 +508,30 @@ impl AgentControl {
         let parent_thread = state.get_thread(*parent_thread_id).await.ok()?;
         parent_thread.codex.session.user_shell().shell_snapshot()
     }
+
+    async fn inherited_exec_policy_for_source(
+        &self,
+        state: &Arc<ThreadManagerState>,
+        session_source: Option<&SessionSource>,
+        child_config: &crate::config::Config,
+    ) -> Option<Arc<crate::exec_policy::ExecPolicyManager>> {
+        let Some(SessionSource::SubAgent(SubAgentSource::ThreadSpawn {
+            parent_thread_id, ..
+        })) = session_source
+        else {
+            return None;
+        };
+
+        let parent_thread = state.get_thread(*parent_thread_id).await.ok()?;
+        let parent_config = parent_thread.codex.session.get_config().await;
+        if !crate::exec_policy::child_uses_parent_exec_policy(&parent_config, child_config) {
+            return None;
+        }
+
+        Some(Arc::clone(
+            &parent_thread.codex.session.services.exec_policy,
+        ))
+    }
 }
 #[cfg(test)]
 #[path = "control_tests.rs"]