PAP-2853 Close 8px flip-gap on mention menu

Align CSS max-height with MENTION_MENU_HEIGHT (208) so the rendered
menu fills the layout-reserved space; previously max-h-[200px] clipped
the box 8px short of the JS layout budget, leaving a visible gap above
the caret line on the flipped path.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/components/MarkdownEditor.tsx

@@ -1220,7 +1220,7 @@ export const MarkdownEditor = forwardRef<MarkdownEditorRef, MarkdownEditorProps>
       {mentionActive && filteredMentions.length > 0 && mentionMenuPosition &&
         createPortal(
           <div
-            className="fixed z-[9999] min-w-[180px] max-w-[calc(100vw-16px)] max-h-[200px] overflow-y-auto rounded-md border border-border bg-popover shadow-md"
+            className="fixed z-[9999] min-w-[180px] max-w-[calc(100vw-16px)] max-h-[208px] overflow-y-auto rounded-md border border-border bg-popover shadow-md"
             style={{
               top: mentionMenuPosition.top,
               left: mentionMenuPosition.left,