gapfill G1: remove 5 ruff F401 unused imports (3 unused os in production files, 2 in tests); no assert lines changed, ruff all cloud now 0

cloud/arch_conformance.py

@@ -74,7 +74,6 @@ stopping at the first.
 """
 
 import ast
-import os
 from pathlib import Path
 
 FOUNDATION_MODULES = frozenset({"db", "models", "queue", "logging_config"})