runtime(doc): Add missing optional tail command-name specs

- Use the optional tail command-name specs at help entries for :keepalt,
  :lcd, :cfdo, :lfdo, :wundo, :rundo, :bdelete and :bunload.
- Add missing shortname tags.

closes: #18547

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

runtime/doc/undo.txt

@@ -1,4 +1,4 @@
-*undo.txt*      For Vim version 9.1.  Last change: 2024 Nov 09
+*undo.txt*      For Vim version 9.1.  Last change: 2025 Oct 11
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -278,8 +278,8 @@ guaranteed.
 
 You can also save and restore undo histories by using ":wundo" and ":rundo"
 respectively:
-							*:wundo* *:rundo*
-:wundo[!] {file}
+							*:wu* *:wundo*
+:wu[ndo][!] {file}
 		Write undo history to {file}.
 		When {file} exists and it does not look like an undo file
 		(the magic number at the start of the file is wrong), then
@@ -292,7 +292,8 @@ respectively:
 		name. So it is not possible to overwrite an existing undofile
 		in a write-protected directory.
 
-:rundo {file}	Read undo history from {file}.
+							*:rund* *:rundo*
+:rund[o] {file}	Read undo history from {file}.
 
 You can use these in autocommands to explicitly specify the name of the
 history file.  E.g.: >