[WIP] Add functionality to send messages to opencode server

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

I need a way of sending a message to the opencode server

I want it to run all his workflow but restrain it to the current file. Instead of editing the file I want the last part of the response to be editing instructions for my current buffer.

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