feat: rename /read-only to /read

[fry69]

fix #1739

Since /read and /read-only gets used interchangeably I think it is time to rename /read-only to only /read to reduce confusion.

Rationale:
/file clearly tells the user that a file should be marked to get edited
/read clearly communicates that the file should only be read, not edited

This is a one-time thing to learn and removes the mental load from often getting auto-corrected to/read-only.

IMHO it is enough to point this out and explain this in the documentation. aider should be as helpful and concise on the command line as possible.

Kinda reverts commit f9471fc

[paul-gauthier]

What's the purpose here? You can type /read foo.ext in the chat already.

[fry69]

The purpose is to get rid of the read-only confusion (it's enough to point that out in the docs IMHO) and not get auto-completed to that, it is a bit annoying and inconsistent.

Feel free to close this you think otherwise though :)