Specify UTF-8 encoding when reading ATOM decision file

Co-authored-by: toolate28 <[email protected]>

Author: Copilot

tests/test_agent_skills.py

@@ -393,7 +393,7 @@ def test_atom_trail_file_created(self, tmp_path, monkeypatch):
         assert decision_file.exists()
 
         # Verify file content
-        with open(decision_file, 'r') as f:
+        with open(decision_file, 'r', encoding='utf-8') as f:
             file_decision = json.load(f)
 
         assert file_decision['atom_tag'] == atom_tag