Feature summary: Allow editnotices to be defined globally on meta, similar to global user pages. $wgGlobalUserPage

Use case(s): A user who is active on multiple Wikimedia wikis wants to display an editnotice on their user talk page across all those wikis. Currently, they must manually create and maintain the editnotice template on every individual wiki. If they update the notice, they have to replicate that change everywhere. The underlying problem is that there is no central place to define a personal editnotice that applies globally, forcing unnecessary duplication of effort.

Benefits: This would be consistent with the existing global user page feature, which already establishes the principle that a user's presence can be managed centrally on Meta. Users active across many wikis would only need to maintain one editnotice.