p2 layout

- _tokens.scss — added --wg-space-2xs…xl (0.25–2rem, 4pt scale), --wg-ledger-line: 1.78rem, --wg-page-width: 1420px.
- Card gaps unified to --wg-space-sm, card interiors to --wg-space-md, the compact topic-list header to --wg-space-xs (_categories.scss, _topics.scss, _widgets.scss, _responsive.scss).
- Ledger ruling height is now one token across topics, posts, pagination, quick-reply, and the composer (_posts.scss, _controls.scss).
- Footer rails now share the topbar's 1420px measure (_footer.scss:36,123,143), so the page's top and bottom edges align.
- Stat tiles got explicit padding instead of inheriting Bootstrap's (_topics.scss:369, _categories.scss:326).
- Documented the scale and rules in DESIGN.md (new "Spacing & Layout" section).

scss/westgate/_responsive.scss

@@ -11,7 +11,7 @@
 	li[component="categories/category"],
 	li[component="category/topic"],
 	li[component="post"] .post-container {
-		padding: 0.85rem !important;
+		padding: var(--wg-space-sm) !important;
 	}
 
 	li[component="categories/category"] h2.title {
@@ -39,7 +39,7 @@
 
 @include media-breakpoint-down(md) {
 	.category-header {
-		padding: 0.85rem;
+		padding: var(--wg-space-sm);
 	}
 
 	li[component="post"] .content,