fix: document_actions title/content helpers crash on non-string input (#1621)

tests/test_document_actions_nonstring.py

@@ -0,0 +1,18 @@
+"""Regression: document_actions title/content helpers must tolerate non-strings.
+
+_norm_title/_content_fingerprint/_real_len used `(x or "")`, which only guards
+falsy; a non-string (e.g. an int) is truthy, so `.strip()`/`re.sub(..., x)`
+raised. They now coerce non-strings to "".
+"""
+from src.document_actions import _norm_title, _content_fingerprint, _real_len
+
+
+def test_non_string_inputs_do_not_crash():
+    assert _norm_title(123) == ""
+    assert _content_fingerprint(123) == ""
+    assert _real_len(["x"]) == 0
+
+
+def test_valid_inputs_unchanged():
+    assert _norm_title("  Hello   World ") == "hello world"
+    assert _real_len("# Title") == len("Title")