fix: builtin_actions heuristics crash on a truthy non-string input (#1639)

tests/test_builtin_actions_nonstring.py

@@ -0,0 +1,21 @@
+"""Regression: builtin_actions heuristics must tolerate non-string input.
+
+_result_has_work did `result.lower()` after a falsy-only guard, and
+_classify_event_heuristic did `(summary or "").lower()`; a truthy non-string
+(e.g. a dict) raised AttributeError. They now coerce/guard non-strings.
+"""
+from src.builtin_actions import _result_has_work, _classify_event_heuristic
+
+
+def test_result_has_work_non_string():
+    assert _result_has_work({"x": 1}) is False
+    assert _result_has_work(123) is False
+
+
+def test_classify_event_heuristic_non_string():
+    out = _classify_event_heuristic(123)
+    assert isinstance(out, tuple)
+
+
+def test_valid_inputs_unchanged():
+    assert _result_has_work("Processed 0 emails") is False