test: remove CodeQL-reported unused imports

Author: cdeust

tests/test_context_guard_hooks.py

@@ -5,7 +5,6 @@
 import importlib.util
 import io
 import json
-import os
 import sys
 from pathlib import Path
 from types import SimpleNamespace

tests/test_statusline_transcript.py

@@ -5,7 +5,6 @@
 import importlib.util
 import io
 import json
-import sys
 from pathlib import Path
 
 

tests/test_subagent_usage.py

@@ -4,7 +4,6 @@
 import json
 import os
 import sys
-from types import SimpleNamespace
 
 sys.path.insert(0, os.path.join(
     os.path.dirname(__file__), "..", "plugins", "context-guard", "tools"))