give class names a prefix on reference pages

fixes processing#650
before: blur reference page would have .blur CSS style applied
after: blur reference page has .reference_blur class name,
so there are no more collisions with CSS styles

hopefully this doesn't have any unintended side effects

src/layouts/ReferenceItemLayout.astro

@@ -82,6 +82,7 @@ const seenParams: Record<string, true> = {};
 
 <BaseLayout
   title={title}
+  titleClass={`reference_${title.toLowerCase()}`}
   subtitle={null}
   variant="item"
   topic="reference"