Apply REPL-style print to student code in unit_test mode

_add_repl_print was called in demo and io_test but not unit_test,
so bare expressions produced no output even after stdout was wired
into feedback.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: m-messer

evaluation_function/evaluation.py

@@ -253,7 +253,7 @@ def _evaluate_unit(response: str, test_code: str, result: Result) -> Result:
 
     results_path = tempfile.mktemp(suffix=".json")
     runner = _UNIT_RUNNER_TEMPLATE.format(results_path=results_path)
-    combined = response + "\n\n" + test_code + runner
+    combined = _add_repl_print(response) + "\n\n" + test_code + runner
     stdout, stderr, timed_out, _ = _run_code(combined, "")
 
     test_results = None