fix: grade decorated Answer markers instead of falling through to prose

src/cura_eval/mcq.py

@@ -34,7 +34,14 @@ def extract_letter(text: str, max_letter: str = "J") -> str | None:
     if boxed:
         return boxed[-1]
 
-    marker = re.findall(rf"(?:FINAL\s+)?ANSWER\s*(?:IS\s+)?[:=]?\s*\(?({cls})\)?\b", cleaned)
+    # Allow a short run of decoration between ANSWER/IS and the letter
+    # (markdown bold "**Answer:** C", em dashes, fullwidth colons, ...).
+    # Without this those replies fall through to the standalone rule below,
+    # where later prose letters silently override the stated answer.
+    marker = re.findall(
+        rf"(?:FINAL\s+)?ANSWER\s*(?:IS\s+)?[^A-Za-z0-9]{{0,6}}\(?({cls})\s*\)?\b",
+        cleaned,
+    )
     if marker:
         return marker[-1]
 

tests/test_mcq.py

@@ -10,6 +10,17 @@ def test_answer_marker():
     assert extract_letter("answer is (E)", "J") == "E"
 
 
+def test_answer_marker_survives_markdown_and_unicode_decoration():
+    # Decorated markers used to miss the Answer rule entirely, so the
+    # standalone last-occurrence fallback grabbed letters from later prose.
+    assert extract_letter("**Answer:** C. Option D was considered and rejected.", "J") == "C"
+    assert extract_letter("**Final Answer:** A\n\nDifferential recap: (B) viral, (C) bacterial.", "J") == "A"
+    assert extract_letter("Final Answer - C\n\nPlan E rejected due to cost.", "J") == "C"
+    assert extract_letter("Answer：E", "J") == "E"
+    assert extract_letter("**The answer is: B**", "J") == "B"
+    assert extract_letter("ANSWER IS :: G", "J") == "G"
+
+
 def test_standalone_letter_last_occurrence():
     assert extract_letter("Could be A or maybe B", "J") == "B"