Function capture 

pub fn capture(prompt: &str) -> Result<Option<String>>

Open the best available editor with comment-prompt instructions.

Uses Git’s editor resolution order:

1. $GIT_EDITOR
2. git config core.editor
3. $VISUAL
4. $EDITOR
5. Built-in TUI editor

prompt lines are prefixed with # and stripped from the result. Returns Some(content) on save, None if cancelled or empty.