[FEATURE]: Recursive permission with external_directory or external_permission

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

The permission external_directory should work exactly like permission just for external directories. So that it is possible to setup opencode.json like this, if the recursive nature is not difficult:

{
  "permission": {
    "*": "allow",
    "edit": {
      "*": "allow",
      "Settings/**": "deny"
    },
    "external_director": {
      "*": "deny",
      "edit": {
        "*": "deny",
        "Temp/**": "allow"
      },
      "read": {
        "*": "deny",
        "~/**": "allow"
      }
    }
  }
}

It would also be fine with:

{
  "permission": {
    "*": "allow",
    "edit": {
      "*": "allow",
      "Settings/**": "deny"
    },
  },
  "external_permission": {
    "*": "deny",
    "edit": {
      "*": "deny",
      "Temp/**": "allow"
    },
    "read": {
      "*": "deny",
      "~/**": "allow"
    }
  }
}