Restore tool cards on thread deserialization (#30053)

Release Notes:

- N/A

---------

Co-authored-by: Julia Ryan <juliaryan3.14@gmail.com>

crates/assistant_tools/src/thinking_tool.rs

@@ -55,7 +55,7 @@ impl Tool for ThinkingTool {
     ) -> ToolResult {
         // This tool just "thinks out loud" and doesn't perform any actions.
         Task::ready(match serde_json::from_value::<ThinkingToolInput>(input) {
-            Ok(_input) => Ok("Finished thinking.".to_string()),
+            Ok(_input) => Ok("Finished thinking.".to_string().into()),
             Err(err) => Err(anyhow!(err)),
         })
         .into()