test(eval_gate): strip ANSI escapes in train --help CI assertion

`test_train_gate_flag_accepted` asserted `"--gate" in result.output`, but
Typer/Click under CI emits ANSI color codes that split the flag name into
non-contiguous chars: `\x1b[1;36m-\x1b[0m\x1b[1;36m-gate\x1b[0m`. The literal
"--gate" substring is never present. All 9 OS × Python combos failed on the
v0.26.0 Parts B-E push.

Fix: strip ANSI via regex before checking. Also assert on "eval-gated" from
the option description to double-check the flag is wired to its help text.

CI-only / tests-only: no soup_cli/ changes, no version bump needed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/test_eval_gate.py

@@ -489,6 +489,12 @@ class TestEvalGateCLI:
 class TestTrainGateFlag:
     def test_train_gate_flag_accepted(self, tmp_path, monkeypatch):
         """The --gate flag must be visible in `soup train --help`."""
+        import re
+
         result = runner.invoke(app, ["train", "--help"])
         assert result.exit_code == 0, (result.output, repr(result.exception))
-        assert "--gate" in result.output
+        # Strip ANSI escape sequences — macOS CI runners emit color codes
+        # that split "--gate" into non-contiguous characters (see commit msg).
+        cleaned = re.sub(r"\x1b\[[0-9;]*m", "", result.output)
+        assert "--gate" in cleaned
+        assert "eval-gated" in cleaned