Custom commands should be able to augment existing prompt gen for format-specific tools

An example use case here is that I'm injecting an "ask-media" command which can be used to ask an LLM to query the contents of media files (images, pdfs etc), and i'd like the file type <-> command association to exist in the same location in the prompt as for the built-in tools.

I also noticed that there are potentially some missing associations, like using sqlite3 for .db and .sqlite3 files