How do I make the exposed filter values available as tokens for text areas
You can show the relevant search term in Text area when you add it to the Header option in Views. 

When you tick the Use replacement tokens from the first row option you will see the Replacement patterns tokens available, and below that global replacement tokens. 

You can use something like: 

&lt;div class="messages messages--status"&gt;Your search of {{ name }} has [view:total-rows] result(s). &lt;/div&gt;


Although you'll probably want to take care of plurals more intelligently and also use a twig conditional to not show anything if the Exposed form isn't used.