Include EditAgent's raw output when inspecting thread (#30337)

This allows us to debug the raw edits that were generated when people
report feedback, when running evals and when opening the thread as
Markdown.

Release Notes:

- Improved debug output for agent threads.

crates/eval/src/instance.rs

@@ -965,6 +965,15 @@ impl RequestMarkdown {
                             messages.push_str("**ERROR:**\n");
                         }
                         messages.push_str(&format!("{}\n\n", tool_result.content));
+
+                        if let Some(output) = tool_result.output.as_ref() {
+                            writeln!(
+                                messages,
+                                "**Debug Output**:\n\n```json\n{}\n```\n",
+                                serde_json::to_string_pretty(output).unwrap()
+                            )
+                            .unwrap();
+                        }
                     }
                 }
             }