[app-server] feat: add old_content and new_content to FileChange update patches

codex-rs/exec/src/event_processor_with_human_output.rs

@@ -406,6 +406,7 @@ impl EventProcessor for EventProcessorWithHumanOutput {
                         FileChange::Update {
                             unified_diff,
                             move_path,
+                            ..
                         } => {
                             let header = if let Some(dest) = move_path {
                                 format!(

codex-rs/exec/tests/event_processor_with_json_output.rs

@@ -823,6 +823,8 @@ fn patch_apply_success_produces_item_completed_patchapply() {
         FileChange::Update {
             unified_diff: "--- c/modified.txt\n+++ c/modified.txt\n@@\n-old\n+new\n".to_string(),
             move_path: Some(PathBuf::from("c/renamed.txt")),
+            old_content: "-old\n".to_string(),
+            new_content: "+new\n".to_string(),
         },
     );
 
@@ -895,6 +897,8 @@ fn patch_apply_failure_produces_item_completed_patchapply_failed() {
         FileChange::Update {
             unified_diff: "--- file.txt\n+++ file.txt\n@@\n-old\n+new\n".to_string(),
             move_path: None,
+            old_content: "-old\n".to_string(),
+            new_content: "+new\n".to_string(),
         },
     );