add-backend-tool

# Add Backend Tool

## Instructions
1. Read `backend/main.py` to understand existing tool patterns:
   - Find the `tools` list with function definitions
   - Review helper functions (read_file, write_file, run_terminal_command, web_search)

2. Create the helper function:
   ```python
   def new_tool_name(param1: str, param2: int = 10) -> str:
       """Docstring explaining the tool."""
       try:
           # Implementation
           return result
       except Exception as e:
           return f"Error: {str(e)}"
   ```

3. Add tool definition to the `tools` list:
   ```python
   {
       "type": "function",
       "function": {
           "name": "new_tool_name",
           "description": "What this tool does and when to use it",
           "parameters": {
               "type": "object",
               "properties": {
                   "param1": {"type": "string", "description": "..."},
                   "param2": {"type": "integer", "description": "..."}
               },
               "required": ["param1"]
           }
       }
   }
   ```

4. Add tool invocation handler in the WebSocket message loop:
   ```python
   elif func_name == "new_tool_name":
       result = new_tool_name(**args)
   ```

5. Update mode restrictions if needed:
   - Agent mode: full access
   - Chat mode: add to allowed list only if read-only/safe

## Examples
- "Add a tool to list directory contents"
- "Create a tool for git operations"
- "Add web scraping capability"

## Guardrails
- Include proper error handling with try/except
- Add timeout for any long-running operations
- Consider security implications (Chat mode restrictions)
- Never hardcode API keys or secrets
- Document the tool's purpose in the function docstring