[Feature request]: add an option to just output a prompt

[stoerr]

What do you need?

I suggest adding a command line option to just output the prompt to stdout or into a file.

Background: There is quite a number of tools that use LLMs from the command line (as discussed here) which have somewhat different focus and do different things well / add different capabilities or tools to the raw LLM. But there is one thing where fabric really stands out and shines: providing a growing library of excellent prompts for many tasks. If it was able to just output the prompts you could make that interoperable with other tools in the best Unix like style.

An interesting point is how to handle that some patterns have a system and user prompt. Perhaps there could be command line options to write the system prompt to a file (- being stdout) and to write the prompt to a file (again - being stdout). Or an option to print the prompt and an option to print the system prompt of the selected pattern, and then use -o to write it to a file if stdout isn't wanted.