Preserve plugin attribution across command approvals (#35029)

## What changed

- Add optional `plugin_id` and `script_path` fields to execution approval and guardian assessment events.
- Propagate validated plugin attribution through delegated approvals, guardian-reviewed command items, app-server notifications, thread history, and rollout traces.
- Preserve attribution on both started and completed command items, including declined commands.

## Testing

- Extend core, app-server, thread-history, and rollout-trace tests to cover plugin attribution propagation and serialization.

GitOrigin-RevId: 723684d010cab04142918d7a95e06ed95d008da1

codex-rs/app-server-protocol/src/protocol/item_builders.rs

@@ -179,8 +179,8 @@ pub fn build_item_from_guardian_event(
             }];
             Some(ThreadItem::CommandExecution {
                 id: id.clone(),
-                plugin_id: None,
-                script_path: None,
+                plugin_id: assessment.plugin_id.clone(),
+                script_path: assessment.script_path.clone(),
                 command,
                 cwd: cwd.clone().into(),
                 process_id: None,
@@ -217,8 +217,8 @@ pub fn build_item_from_guardian_event(
             };
             Some(ThreadItem::CommandExecution {
                 id: id.clone(),
-                plugin_id: None,
-                script_path: None,
+                plugin_id: assessment.plugin_id.clone(),
+                script_path: assessment.script_path.clone(),
                 command,
                 cwd: cwd.clone().into(),
                 process_id: None,