refactor: require explicit sqlite paths

tests/test_store_sqlite.py

@@ -2,9 +2,16 @@ import pathlib
 import tempfile
 import uuid
 
+import pytest
+
 from agentmsgs.stores.sqlite import SQLiteStore
 
 
+def test_sqlite_store_requires_explicit_path():
+    with pytest.raises(TypeError):
+        SQLiteStore()
+
+
 def test_sqlite_persists_across_handles():
     with tempfile.TemporaryDirectory() as d:
         p = pathlib.Path(d) / "test.db"