assistant: Add support for claude-3-7-sonnet-thinking (#27085)

Closes #25671

Release Notes:

- Added support for `claude-3-7-sonnet-thinking` in the assistant panel

---------

Co-authored-by: Danilo Leal <daniloleal09@gmail.com>
Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Agus Zubiaga <hi@aguz.me>

crates/assistant_eval/src/eval.rs

@@ -120,7 +120,7 @@ impl Eval {
                     .count();
                 Ok(EvalOutput {
                     diff,
-                    last_message: last_message.text.clone(),
+                    last_message: last_message.to_string(),
                     elapsed_time,
                     assistant_response_count,
                     tool_use_counts: assistant.tool_use_counts.clone(),