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)

simple_test_cli_README.md

@@ -0,0 +1,84 @@
+# Simple Test CLI for MCP-Forge
+
+A minimal testing tool for MCP-Forge execution backends.
+
+## Features
+
+✅ **Working:**
+- Simple (stateless) backend with one-shot and interactive execution
+- No security restrictions (for testing only)
+- No resource limits (avoids cgroupv2 issues in rootless Podman)
+
+❌ **Not Working:**
+- Jupyter (stateful) backend - has connection file timing issues
+- MCP tool injection - not supported in this simplified version
+
+## Usage
+
+### One-Shot Execution (Simple Backend)
+
+```bash
+# Execute Python code and exit
+./simple_test_cli.py --execute 'print(2 + 2)'
+
+# More complex code
+./simple_test_cli.py --execute 'x = [1, 2, 3]; print(sum(x))'
+```
+
+### Interactive REPL (Simple Backend)
+
+```bash
+# Start interactive shell
+./simple_test_cli.py
+
+# In the shell:
+>>> x = 42
+>>> print(x * 2)
+84
+>>> .exit
+```
+
+### Special Commands
+
+- `.exit`, `.quit` - Exit the shell
+- `.help` - Show help
+- `.clear` - Clear screen
+
+## Requirements
+
+- Rootless Podman with user socket at `$XDG_RUNTIME_DIR/podman/podman.sock`
+- Container images built:
+  - `mcp-forge/python:3.12` - For simple backend
+  - `mcp-forge/jupyter:latest` - For Jupyter backend (not working yet)
+
+## Limitations
+
+This is a **testing tool only**:
+- No security validation
+- No resource limits
+- No MCP tool injection
+- No proper error handling for production use
+- Jupyter backend has connection file issues
+
+For production use, use the full MCP-Forge server with proper configuration.
+
+## Testing Containers
+
+To test if containers work:
+
+```bash
+# Test simple execution
+./test_containers.py
+
+# Should output:
+# ✓ Simple Execution: PASS
+# ✓ Jupyter Kernel: PASS
+```
+
+## Architecture
+
+- `PassthroughValidator` - Dummy validator that allows all operations
+- `SimpleExecutorWrapper` - Wraps CodeExecutor, skips resource limits
+- `JupyterKernelWrapper` - Wraps JupyterKernelManager (has issues)
+
+The CLI creates temporary directories for logs and connection files, cleans up on exit.