Expose whether an embedded surface is at a semantic prompt

[figelwump]

What do you want to change?

I'm building Toastty, a native macOS app for coding with agents that embeds Ghostty (https://github.com/figelwump/toastty)

I'd like to add a function to expose whether an embedded surface is currently at a semantic prompt. Here is the change in my fork of Ghostty: figelwump@afce990 (Note this is based on an older Ghostty revision; I'll update as needed based on the latest before submitting a PR if you are ok with the approach.)

This change is what I use in Toastty and as such has shipped in multiple Toastty production releases.

Why do you want to make this change?

Toastty needs this signal to prevent a user from sending managed agent commands into a terminal that is already busy. Having this be part of mainline Ghostty would make it easier for Toastty contributors.

I acknowledge that:

• I have read the Contributing Guide and understand the contribution process.
• I have read and agree to follow the AI Usage Policy.
• I wrote this vouch request myself, in my own voice, without AI generating it.

[jcollie]

!vouch

[jcollie]

What you have so far seems fine, but we should also expose this to libghostty-vt.

[figelwump]

Sounds good. I can expose the same Terminal.cursorIsAtPrompt() result through libghostty-vt as well.