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/_topbar.scss

@@ -28,7 +28,7 @@ $wg-topbar-panel-bg: linear-gradient(
   grid-template-columns: auto minmax(0, 1fr) auto;
   align-items: center;
   gap: 0.9rem;
-  width: min(100%, 1420px);
+  width: min(100%, var(--wg-page-width));
   min-height: 64px;
   margin: 0 auto;
   padding: 0.55rem clamp(0.85rem, 2vw, 1.5rem);