fix: research query misclassifies 'whatsapp'/'however' as questions (#1247)

* fix: detect question words as whole words, not prefixes

* fix: same question-word prefix bug in the services search copy

* test: question-word detection rejects prefix lookalikes

tests/test_question_type_detection.py

@@ -0,0 +1,18 @@
+"""Tests for question-word detection in research query enhancement."""
+
+from src.search.query import _detect_question_type
+
+
+def test_whole_word_questions_detected():
+    assert _detect_question_type("what is topological data analysis") == "what"
+    assert _detect_question_type("how do transformers work") == "how"
+    assert _detect_question_type("why") == "why"
+
+
+def test_prefix_lookalikes_not_misclassified():
+    # Regression: a bare prefix used to flag these as questions and append
+    # spurious boost terms in enhance_query.
+    assert _detect_question_type("whatsapp pricing") is None
+    assert _detect_question_type("however we proceed") is None
+    assert _detect_question_type("whole foods stock") is None
+    assert _detect_question_type("howard stern show") is None