test(code_mode): add intended truncation warning to stale expectation

truncate_code_mode_result intentionally prepends 'Warning: truncated output
(original token count: N)' (confirmed by the passing unit test
truncated_text_output_starts_with_warning); the printf-based integration
expectation predated it. The 5 python3-based code_mode tests fail only on this
box due to partial exec stdout capture (ACTUAL_LEN=11980 vs 50000 — the
documented skip_if_wine_exec class); they pass in CI's full-capture Linux.

codex-rs/core/tests/suite/code_mode.rs

@@ -964,7 +964,7 @@ text(result.output);
             &custom_tool_output_items(&second_mock.single_request(), "call-1"),
             /*index*/ 1
         ),
-        "Total output lines: 1\n\n0123456789…5 tokens truncated…0123456789"
+        "Warning: truncated output (original token count: 10)\nTotal output lines: 1\n\n0123456789…5 tokens truncated…0123456789"
     );
 
     Ok(())