runtime: set 'cpoptions' for line-continuation in various runtime files

closes: #17121

Signed-off-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/ftplugin/mojo.vim

@@ -2,12 +2,16 @@
 " Language:	Mojo
 " Maintainer:	Riley Bruins <ribru17@gmail.com>
 " Last Change:	2024 Jul 07
+" 2025 Apr 16 by Vim Project (set 'cpoptions' for line continuation, #17121)
 
 if exists('b:did_ftplugin')
   finish
 endif
 let b:did_ftplugin = 1
 
+let s:cpo_save = &cpo
+set cpo&vim
+
 setlocal include=^\\s*\\(from\\\|import\\)
 setlocal define=^\\s*\\(\\(async\\s\\+\\)\\?def\\\|class\\)
 
@@ -39,3 +43,6 @@ let b:undo_ftplugin = 'setlocal include<'
       \ . '|setlocal suffixesadd<'
       \ . '|setlocal comments<'
       \ . '|setlocal commentstring<'
+
+let &cpo = s:cpo_save
+unlet s:cpo_save