runtime(vim): Update base syntax, contain user command replacement text

Ensure that :command replacement text terminates at the end of the
logical line.

Add :command to the generator exclusion list.

fixes: #18414 (@Dougaak)
fixes: #18448 (Maxim Kim)
closes: #18415

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/generator/gen_syntax_vim.vim

@@ -1,7 +1,7 @@
 " Vim syntax file generator
 " Language:		 Vim script
 " Maintainer:  Hirohito Higashi (h_east)
-" Last Change: 2025 Sep 23
+" Last Change: 2025 Sep 27
 
 let s:keepcpo= &cpo
 set cpo&vim
@@ -307,6 +307,7 @@ function s:get_vim_command_type(cmd_name)
 		catch
 		chdir
 		class
+		command
 		copy
 		debuggreedy
 		def

runtime/syntax/generator/vim.vim.base

@@ -863,6 +863,7 @@ syn region	vimUserCmdReplacement contained
       \ skip=+\n\s*\%(\\\|["#]\\ \)+
       \ end="$"
       \ contains=@vimContinue,@vimUserCmdList,vimComFilter
+      \ keepend
 syn region	vimUserCmdBlock	    contained
       \ matchgroup=vimSep
       \ start="{"