Edit: Handle conflicting diff decorations

[umpox]

Description

Closes https://linear.app/sourcegraph/issue/CODY-4601/disable-autoedits-for-lines-affected-by-edit-command

This PR:

• Fixes an issue where the diff output of an Edit command would conflict with the diff output of an AutoEdit
• Fixes an issue where the diff output of an Edit command would conflict with a command hint (e.g. Opt+K to Edit)

We resolve this by assuming that we will not show any other decorations whilst the edit diff output is present.

Test plan

1. Trigger an Edit command, ensure the diff is visible
2. Attempt to trigger an AutoEdit (e.g. change some code)
3. Attempt to trigger a command hint (e.g. highlight some text)

[umpox]

@valerybugakov @hitesh-1997 Tagging for early review here.

This works by ensuring we do not show any other decorations when the Edit output is present.

It's fixes the problem, but I think we should consider unifying all of our decoration logic into a central place (e.g. DecorationManager) as they are all implicitly linked to each other in the UX. We could then track what decorations are visible there and handle it more explicitly. That's a bigger bit of work, but something to consider if we find ourselves running into any issues

[valerybugakov]

I think we should consider unifying all of our decoration logic into a central place

Yes, that sounds great! It will also make it easier to reuse decoration-related logic across different features.

[valerybugakov]

LGTM! Thanks for the quick fix.