Add test CLI tools for executor testing

- simple_test_cli.py: Working CLI for simple (stateless) backend
  - Supports one-shot execution and interactive REPL
  - Uses PassthroughValidator and wrappers to bypass security for testing
  - Skips resource limits to avoid cgroupv2 issues in rootless Podman
- test_containers.py: Container verification script (all tests passing)
- simple_test_cli_README.md: Documentation for test tools

Note: Jupyter backend has connection file timing issues (future work)

test_containers.py

@@ -0,0 +1,132 @@
+#!/usr/bin/env python3
+"""
+Minimal test script to verify container execution works.
+
+This tests the basic container creation and execution without
+using the full MCP-Forge stack.
+"""
+
+import sys
+import subprocess
+from pathlib import Path
+
+# ANSI colors
+GREEN = "\033[92m"
+RED = "\033[91m"
+GRAY = "\033[90m"
+RESET = "\033[0m"
+
+
+def test_simple_execution():
+    """Test simple container execution."""
+    print(f"\n{GRAY}Testing simple (stateless) execution...{RESET}")
+    
+    code = "print('Hello from MCP-Forge!')\nprint(2 + 2)"
+    
+    cmd = [
+        "podman", "run", "--rm",
+        "--network=none",
+        "mcp-forge/python:3.12",
+        "python3", "-c", code
+    ]
+    
+    try:
+        result = subprocess.run(
+            cmd,
+            capture_output=True,
+            text=True,
+            timeout=10
+        )
+        
+        if result.returncode == 0:
+            print(f"{GREEN}✓ Simple execution works!{RESET}")
+            print(f"{GRAY}Output:{RESET}")
+            print(result.stdout)
+            return True
+        else:
+            print(f"{RED}✗ Simple execution failed{RESET}")
+            print(f"{RED}Error:{RESET}")
+            print(result.stderr)
+            return False
+            
+    except subprocess.TimeoutExpired:
+        print(f"{RED}✗ Execution timed out{RESET}")
+        return False
+    except Exception as e:
+        print(f"{RED}✗ Error: {e}{RESET}")
+        return False
+
+
+def test_jupyter_kernel():
+    """Test Jupyter kernel container."""
+    print(f"\n{GRAY}Testing Jupyter kernel availability...{RESET}")
+    
+    cmd = [
+        "podman", "run", "--rm",
+        "--network=host",
+        "mcp-forge/jupyter:latest",
+        "python3", "-c", "import ipykernel; print(ipykernel.__version__)"
+    ]
+    
+    try:
+        result = subprocess.run(
+            cmd,
+            capture_output=True,
+            text=True,
+            timeout=10
+        )
+        
+        if result.returncode == 0:
+            version = result.stdout.strip()
+            print(f"{GREEN}✓ Jupyter kernel available (ipykernel {version})!{RESET}")
+            return True
+        else:
+            print(f"{RED}✗ Jupyter kernel check failed{RESET}")
+            print(f"{RED}Error:{RESET}")
+            print(result.stderr)
+            return False
+            
+    except subprocess.TimeoutExpired:
+        print(f"{RED}✗ Check timed out{RESET}")
+        return False
+    except Exception as e:
+        print(f"{RED}✗ Error: {e}{RESET}")
+        return False
+
+
+def main():
+    """Main entry point."""
+    print(f"{GREEN}MCP-Forge Container Tests{RESET}")
+    print(f"{GRAY}{'='*40}{RESET}")
+    
+    results = []
+    
+    # Test simple execution
+    results.append(("Simple Execution", test_simple_execution()))
+    
+    # Test Jupyter kernel
+    results.append(("Jupyter Kernel", test_jupyter_kernel()))
+    
+    # Summary
+    print(f"\n{GRAY}{'='*40}{RESET}")
+    print(f"{GREEN}Test Summary:{RESET}\n")
+    
+    passed = sum(1 for _, result in results if result)
+    total = len(results)
+    
+    for name, result in results:
+        status = f"{GREEN}✓ PASS{RESET}" if result else f"{RED}✗ FAIL{RESET}"
+        print(f"  {name}: {status}")
+    
+    print(f"\n{GRAY}Passed: {passed}/{total}{RESET}")
+    
+    if passed == total:
+        print(f"\n{GREEN}All tests passed!{RESET}")
+        return 0
+    else:
+        print(f"\n{RED}Some tests failed.{RESET}")
+        return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())