Maybe nobody knows how to create a patch?
I think the cleanest way to implement the config change required here is just to add the following section to InitialiseSettings.php:
'wgProofreadPagePageJoiner' => [ 'default' => '-', 'zhwikisource' => "__PAGEJOIN__", // T205826 ],
AFAICS, "__PAGEJOIN__" and "__PAGESEPARATOR__" are "magic" strings expected never to appear explicitely in the wikicode of any page in the Page namespace.
Until the T104566 is disabled in this (or another) way in zh.ws, we have few broken pages there.
And actually the T104566 seems to be useless in zh.ws and ja.ws at the moment: no need to remove the page separator when joining words as wgProofreadPagePageSeparator is set to the empty string there.