feature: send prompt in a new session

[lungsin]

Prerequisites

• I searched the docs
• I searched existing issues

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

One of the most common usecase that I have with this plugin is creating a little session to tweak. Something like a Ctrl+k feature from Cursor (not sure if it still has it). Previously on opencode v1, I was using new_session tui command, before sending the prompt. Unfortunately, opencode v2 removed the tui API, so we kinda have to target the session API.

Describe the solution you'd like

Add an option to the ask(default, opts) on whether to append the prompt to the latest session (like the current behaviour), or create a new session with that prompt.

I tested this on a local fork, but by default the create new session API will use a model from opencode go (even if you're using other providers and don't have subscription from opencode go). So, from our side, we have to know what model on that session. I'm proposing the following heuristic:

• Use the model from the latest session
• If there's no session, open a picker popup to let the user pick the model

Describe alternatives you've considered

None, the solution space is quite limited.

Additional context

https://opencode.ai/v2/docs/api#session.create
https://opencode.ai/v2/docs/api#session.switchModel
https://opencode.ai/v2/docs/api#model.list

[nickjvandyke]

Thanks for submitting this idea! It was on my mind too. Idk the best interface for it yet, but definitely one way or another.

Related: #334