This is a very valuable use case for me personally. I frequently have the problem that I change things on the filesystem in a separate tab and the agent context gets out of sync. It fails on subsequent edits, often tries to reverse the changes that I made, and many times I have to copy/paste the command I ran and it's output back into the agent window.

Your complaint is likely a product design decision rather than a engineering capacity prioritization one. As you've noted the fix is pretty trivial. I imagine that some designer or product person is intentionally holding this back for one reason or another