refactor(tests): Add strict type hints to fifth batch of test files

conductor/tests/diag_subagent.py

@@ -2,7 +2,7 @@ import subprocess
 import sys
 import os
 
-def run_diag(role, prompt):
+def run_diag(role: str, prompt: str) -> str:
  print(f"--- Running Diag for {role} ---")
  cmd = [sys.executable, "scripts/mma_exec.py", "--role", role, prompt]
  try: