feature: nested nvim instance with `<c-x>e`

Did you check the docs?

• [x] I have read all the docs

Is your feature request related to a problem? Please describe.

When using the default <c-x>e binding in opencode, it will open the prompt in your $EDITOR. When using this binding inside a nvim terminal (with opencode.nvim's provider being terminal), this results in a nested nvim instance.

Describe the solution you'd like

Ideally, it should just use a buffer and not open a completly different instance.

Describe alternatives you've considered

/

Additional context

No response