Implement manual tool call approval

I think this is a prerequisite for #9 (maybe). If you have an eca config that looks like this:

```json
{
 ...
  "toolCall": {
    "manualApproval": [
      "eca_edit_file"
    ]
 
}
```

The screen hangs with 

`⏳ Waiting for tool call approval`

Doing a grep through the code there doesn't look like a way to approve tools.