I thought there have to be an easier way to achieve this. And it turns out, there is (at least on zsh / macOS). It's just a one-liner prompt and an alias command to add to your .zshrc. After that, '@ run ffmpeg to convert my.mov to mp4' will be converted to the actual command, ready to press Enter.
An interesting side effect is that your '@ whatever' commands become a part of the shell history, so you can rerun them again as regular shell commands.
The entire repo above is simply a README. Just point Claude Code to it and it will install it for you.