fix: Optimize the event handling for inserting variable shortcuts, resolving incorrect blur issues (#22981) (#23707)

web/app/components/workflow/nodes/tool/components/mixed-variable-text-input/placeholder.tsx

         <div className='system-kbd mx-0.5 flex h-4 w-4 items-center justify-center rounded bg-components-kbd-bg-gray text-text-placeholder'>/</div>
         <div
           className='system-sm-regular cursor-pointer text-components-input-text-placeholder underline decoration-dotted decoration-auto underline-offset-auto hover:text-text-tertiary'
-          onClick={((e) => {
+          onMouseDown={((e) => {
+            e.preventDefault()
             e.stopPropagation()
             handleInsert('/')
           })}