fix: agent_tools._truncate crashes on non-string input (#1624)

* fix: agent_tools._truncate crashes on non-string input

* fix: agent_tools._truncate returns a string for non-string input, not the raw value

tests/test_agent_tools_truncate_nonstring.py

@@ -0,0 +1,24 @@
+"""Regression: agent_tools._truncate must always return a string.
+
+It did `len(text)` directly, so `_truncate(None)` raised TypeError. Returning
+the raw non-string just moves the crash downstream (callers treat it as text),
+so non-strings are now coerced to a string and still truncated.
+"""
+from src.agent_tools import _truncate
+
+
+def test_non_string_coerced_to_string():
+    assert _truncate(None) == ""
+    assert _truncate(123) == "123"
+    assert isinstance(_truncate({"a": 1}), str)
+
+
+def test_non_string_is_also_truncated():
+    out = _truncate(12345, limit=3)
+    assert out.startswith("123") and "truncated" in out
+
+
+def test_string_truncation_unchanged():
+    assert _truncate("hello", limit=100) == "hello"
+    out = _truncate("x" * 50, limit=10)
+    assert out.startswith("x" * 10) and "truncated" in out