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/agent/src/thread.rs

@@ -2487,6 +2487,13 @@ impl Thread {
 
                 writeln!(markdown, "**\n")?;
                 writeln!(markdown, "{}", tool_result.content)?;
+                if let Some(output) = tool_result.output.as_ref() {
+                    writeln!(
+                        markdown,
+                        "\n\nDebug Output:\n\n```json\n{}\n```\n",
+                        serde_json::to_string_pretty(output)?
+                    )?;
+                }
             }
         }