Padding is called Spacing

The heading only. What it does is unchanged for now — the word is widening ahead of the behaviour,
which is the right order: the section is about to hold more than one kind of space, and Padding names
only one of them.

web/sections/LayoutPanel.tsx

@@ -357,7 +357,7 @@ export const LayoutPanel = () => {
           </AccordionContent>
         </AccordionItem>
         <AccordionItem value="padding" className="rounded-lg border border-border px-4">
-          <AccordionTrigger className="text-xs">Padding</AccordionTrigger>
+          <AccordionTrigger className="text-xs">Spacing</AccordionTrigger>
           <AccordionContent>
                 {/*
                   The site's gutter, not a per-band padding.