runtime(doc): Improve doc for cmdline-autocomplete

Maybe this was unnecessary, but saw this:
vim/vim#17854

Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: girishji

runtime/doc/builtin.txt

@@ -1,4 +1,4 @@
-*builtin.txt*	For Vim version 9.1.  Last change: 2025 Aug 06
+*builtin.txt*	For Vim version 9.1.  Last change: 2025 Aug 08
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -12353,6 +12353,11 @@ wildtrigger()						*wildtrigger()*
 		To retain normal history navigation (up/down keys): >
 			cnoremap <Up>   <C-U><Up>
 			cnoremap <Down> <C-U><Down>
+<
+		To set an option specifically when performing a search, e.g.
+		to set 'pumheight': >
+			autocmd CmdlineEnter [/\?] set pumheight=8
+			autocmd CmdlineLeave [/\?] set pumheight&
 <
 		Return value is always 0.
 

runtime/doc/cmdline.txt

@@ -1,4 +1,4 @@
-*cmdline.txt*   For Vim version 9.1.  Last change: 2025 Jul 21
+*cmdline.txt*   For Vim version 9.1.  Last change: 2025 Aug 08
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -927,7 +927,7 @@ to insert special things while typing you can use the CTRL-R command.  For
 example, "%" stands for the current file name, while CTRL-R % inserts the
 current file name right away.  See |c_CTRL-R|.
 
-Note:  If you want to avoid the effects of special characters in a Vim script
+Note: If you want to avoid the effects of special characters in a Vim script
 you may want to use |fnameescape()|.  Also see |`=|.
 
 
@@ -1325,8 +1325,10 @@ Example: >
 	:au CmdwinLeave :  let &cpt = b:cpt_save
 This sets 'complete' to use completion in the current window for |i_CTRL-N|.
 Another example: >
-	:au CmdwinEnter [/?]  startinsert
+	:au CmdwinEnter [/\?]  startinsert
 This will make Vim start in Insert mode in the command-line window.
+Note: The "?" needs to be escaped, as this is a |file-pattern|.  See also
+|cmdline-autocompletion|.
 
 						*cmdwin-char*
 The character used for the pattern indicates the type of command-line: