Sections and Footer get a Gap, three fields across

The room between a band's columns: gap-8 in a two-column section, gap-x-24
gap-y-10 in the footer. Both were written into the template that drew them.

The canvas now SKIPS a utility nothing has chosen instead of stripping it. The
old rule lied twice — a section's own padding vanished while the panel was open,
and a band with no chosen gap lost the site's default.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/canvas.ts

@@ -599,14 +599,13 @@ export function paintMeasure(document: Document): () => void {
  * header, `py-*` from a band. Everything else on the element survives, which is what makes it safe to
  * do this to a `<header>` carrying a border and a background as well.
  *
- * The one exception is a SECTION, whose own padding is also a `px-*` on the marked element — so while
+ * A target with nothing chosen is skipped entirely — see the note in the loop. That is what keeps a
- * the panel is open its padding reads as the site gutter. Harmless on the layout page, whose bands have
+ * section's own padding, and the site's default gap, from disappearing while the panel is open.
- * none, and that page is the only one this runs against.
  */
 export type SpacingDraft = {
   header?: { paddingX?: Steps; marginBottom?: Steps };
-  sections?: { paddingX?: Steps; paddingY?: Steps };
+  sections?: { paddingX?: Steps; paddingY?: Steps; gap?: Steps };
-  footer?: { paddingX?: Steps; marginTop?: Steps };
+  footer?: { paddingX?: Steps; marginTop?: Steps; gap?: Steps };
 };
 
 export type Steps = Partial<Record<'base' | 'md' | 'lg', number>>;
@@ -630,6 +629,8 @@ const TARGETS = [
   { selector: '[data-gutter="footer"]', utility: 'px', read: (s: SpacingDraft) => s.footer?.paddingX },
   { selector: '[data-space="header"]', utility: 'mb', read: (s: SpacingDraft) => s.header?.marginBottom },
   { selector: '[data-space="footer"]', utility: 'mt', read: (s: SpacingDraft) => s.footer?.marginTop },
+  { selector: '[data-gap="sections"]', utility: 'gap', read: (s: SpacingDraft) => s.sections?.gap },
+  { selector: '[data-gap="footer"]', utility: 'gap', read: (s: SpacingDraft) => s.footer?.gap },
 ] as const;
 
 export function applySpacing(document: Document, spacing: SpacingDraft): () => void {
@@ -639,6 +640,16 @@ export function applySpacing(document: Document, spacing: SpacingDraft): () => v
     const pattern = new RegExp(`^(?:md:|lg:)?${target.utility}-\\d+$`);
     const classes = scaleClasses(target.utility, target.read(spacing)).split(/\s+/).filter(Boolean);
 
+    /*
+      Nothing chosen means DON'T TOUCH IT, rather than strip it.
+
+      Stripping was the old rule and it lied twice: a section's own `px-*` vanished while the panel was
+      open, and a band with no chosen gap lost the site's default `gap-8` — so the preview showed a
+      layout the page would never render. What the panel is drafting is an override, and an override
+      that has not been set is not an instruction to remove anything.
+    */
+    if (!classes.length) continue;
+
     for (const element of document.querySelectorAll<HTMLElement>(target.selector)) {
       touched.push([element, element.className]);
       const kept = element.className.split(/\s+/).filter((name) => name && !pattern.test(name));

web/sections/SpacingTab.tsx

@@ -46,6 +46,7 @@ const BANDS = [
     fields: [
       { key: 'paddingX' as const, label: 'Horizontal padding' },
       { key: 'paddingY' as const, label: 'Vertical padding' },
+      { key: 'gap' as const, label: 'Gap' },
     ],
   },
   {
@@ -54,6 +55,7 @@ const BANDS = [
     fields: [
       { key: 'paddingX' as const, label: 'Horizontal padding' },
       { key: 'marginTop' as const, label: 'Margin top' },
+      { key: 'gap' as const, label: 'Gap' },
     ],
   },
 ];
@@ -94,7 +96,9 @@ export const SpacingTab = ({
       {BANDS.map((band) => (
         <div key={band.key} className="flex flex-col gap-2">
           <h4 className="text-xs font-medium">{band.label}</h4>
-          <div className="grid grid-cols-1 gap-3 @[20rem]:grid-cols-2">
+          {/* Three across, and the same grid for every band — Top Nav has two fields and leaves the
+              third empty, so the columns line up down the section rather than staggering. */}
+          <div className="grid grid-cols-1 gap-3 @[26rem]:grid-cols-3">
             {band.fields.map((field) => {
               const current = (spacing as Record<string, Record<string, Steps> | undefined>)[band.key]?.[field.key];
               const own = current?.[key];