I pushed it to my personal github repo;
https://github.com/kevinhendricks/Sigil
You want:
Sigil/src/Dialogs/DeleteFiles.*
Sigil/src/Dialogs/WrapWordAnyItemDelegate.*
And Sigil/src/Form_Files/DeleteFiles.ui
The smarts are in the delegate but had to create my own replacement for built in resizeRowsToContents() using a loop and individual row resizing as that call ignored the delegate completely (had to read the qtableview.cpp source to find that little tidbit out)!
Then had to trigger my routine in resize events and set it initially after the constructor was done (ie effectively what you did with show).
Hope this helps.