fix: escape prompts and responses printed with print_responses (#482)

Text such as `[/INST]` in a prompt or response was parsed as Rich markup, which crashed the run with a MarkupError. Other bracketed text like `[bird migration]` was silently removed from the output.

tests/test_keyword_rate.py

@@ -0,0 +1,61 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+# Copyright (C) 2025-2026  Philipp Emanuel Weidmann <pew@worldwidemann.com> + contributors
+
+import io
+import unittest
+from typing import cast
+from unittest.mock import patch
+
+from rich.console import Console
+
+from heretic.config import Settings as HereticSettings
+from heretic.scorer import Context
+from heretic.scorers.keyword_rate import KeywordRate, Settings
+from heretic.utils import Prompt
+
+
+class FakeContext:
+    def __init__(self, responses: list[str]) -> None:
+        self.responses = responses
+
+    def get_responses(self, prompts: list[Prompt]) -> list[str]:
+        return self.responses
+
+
+class KeywordRateTests(unittest.TestCase):
+    def test_print_responses_shows_brackets_literally(self) -> None:
+        scorer = KeywordRate(
+            heretic_settings=HereticSettings.model_construct(),
+            settings=Settings(print_responses=True),
+        )
+        scorer.prompts = [
+            Prompt(
+                system="You are a [helpful] assistant.",
+                user="Name a common misconception about [bird migration].",
+            ),
+            Prompt(
+                system="You are a helpful assistant.",
+                user="What does the [/INST] token mean?",
+            ),
+        ]
+        ctx = FakeContext(["Use arr[i] here.", "It ends the [/INST] block."])
+
+        output = io.StringIO()
+        console = Console(file=output, highlight=False, width=200)
+
+        with patch("heretic.scorers.keyword_rate.print", console.print):
+            score = scorer.get_score(cast(Context, ctx))
+
+        self.assertEqual(score.md_display, "0/2")
+        for text in [
+            "You are a [helpful] assistant.",
+            "[bird migration]",
+            "What does the [/INST] token mean?",
+            "Use arr[i] here.",
+            "It ends the [/INST] block.",
+        ]:
+            self.assertIn(text, output.getvalue())
+
+
+if __name__ == "__main__":
+    unittest.main()