Looks good for me.
Looks good to me. Good job.
Facet fields are locked when ajax is used.
All fields are available, but after the first use and refreshing the results, all fields are locked. I think this is due to the fact that there was a problem with ajax when the user selected the value of another field immediately without waiting for the changed value of the first field to load. And that's why disabled was added for all fields until the ajax works completely. But because of this another strange problem arose - after the first modified field is processed, the result is updated with ajax, but the fields do not stop being disabled.
Sorry for the previous comment, the patch is not quite correct for the core. This one should work.
Comment 9 helped me, I decided to make a patch for those who will be looking for a quick fix.
Please review this patch.