Based on comments, it looks like there might be some sort of bug in your version of Git. A simple git reset (with no arguments at all) should have undone the problem, but in fact you had to remove the index file first, then reset:
rm .git/index
git reset
This git reset will re-build the index file from scratch, now that it's missing. This should be unnecessary. (Note also that the location of the index file depends on whether this is an added work-tree from git worktree add; the above assumes it's not.)
(One potential possible cause for this is that Windows has modes in which it refuses to let a program write to a file.1 But that should show up as an error when running git reset. It might also prevent removing the file, in which case rm .git/index would fail too. So it's not at all clear what is going on here.)
Original answer below.
1Windows has something called "mandatory file locks". Programs cannot avoid these locks. Linux in general has only advisory file locking, although there are some Linux file systems that have extra features. See, e.g., How do I make Windows file-locking more like UNIX file-locking?
As matt said in a comment, this means that you've had Git delete the index copy of these files. Therefore, comparing the HEAD commit to the proposed next commit, the difference will be—if you actually commit right now—that those files won't be in the next commit, i.e., between those two commits, you've deleted the files.
To put one file back, follow the instructions that git status printed:
(use "git restore --staged <file>..." to unstage)
i.e., run:
git restore --staged nta/executor/.gitignore
to copy the HEAD copy of nta/executor/.gitignore back into Git's index. Now the HEAD copy and the index's proposed-next-commit copy match, and git status will no longer mention the file. Repeat for each file as needed.
If you prefer, you can en-masse overwrite the entire index (the entire proposed next commit) from the current commit with:
git reset
(or git reset --mixed, but --mixed is the default).
If you've carefully copied some particular file into the index, this will overwrite that carefully-copied file in the index, and you may have to re-copy it carefully again, to get the effect you so carefully set up. But usually, we tend to copy whatever we have in our work-trees, into the index, so wiping out the index copy this way is not a big deal.
I tried using the suggested method to unstage these changes ... This worked on some of the files, but many others remain listed as deleted.
We could use more detail on this, such as an actual cut-and-paste of the before-and-after git status (or parts of it) and the chosen git restore command. It definitely should go back to the state it had in the HEAD commit, after which git status should be quiet about it.