The unification was discussed here
https://ce.wikipedia.org/wiki/%D0%92%D0%B8%D0%BA%D0%B8%D0%BF%D0%B5%D0%B4%D0%B8:%D0%A4%D0%BE%D1%80%D1%83%D0%BC/%D0%99%D1%83%D0%BA%D1%8A%D0%B0%D1%80%D0%B0#Change_namespace
@Umar: Hi, what is this task asking for? Creating two new namespaces? Or changing some existing namespaces (which ones)?
You linked https://ce.wikipedia.org/wiki/Википеди:Форум#Change_namespace and that does not mention Википеди йийцар or Ков дийцар. Where was this discussed?
You can see the current namespaces at https://ce.wikipedia.org/w/api.php?action=query&meta=siteinfo&siprop=namespaces
I understand this request. The community decided to fix the grammar of the word for "talk". This particular task is for custom namespaces that appear on Wikipedia and not generally for MediaWiki. I'll take care of it.
NS_PROJECT_TALK => '{{GRAMMAR:genitive|$1}}_дийцар',
If this is a project, it will be correct "Проект_йийцар"
removing tag as this is not in Q1 priorities (July 2025- Sep 2025), might need to revisit later