[Feature] recognize when a textarea does not accept input

[jdoconnor]

Summary

Noticed on a github page while browsing a file. Tabby will suggest words at the end of a file when the file is read only

Problem

user confusion

Proposed direction

stronger decision making on whether or not this is an editable field

Additional context

Add mockups, examples, related apps, or constraints here if useful.

[FuJacob]

Thanks, curr taking a look at this!