Apply remaining audit fixes; document radii and code palette in DESIGN.md

- Token sweep: exact-value gold literals now use --wg-border /
  --wg-border-soft / --wg-focus
- Topbar: drop invalid role="menuitem" (no parent role="menu")
- topics_list: topic-select icons get role="checkbox", tabindex,
  aria-label; client.js makes them keyboard-operable and syncs
  aria-checked
- category.tpl: copy-handle link gets an accessible name, "View
  Original" moved to i18n, external-link icon aria-hidden, stretched
  link inside aria-hidden alert removed from tab order
- Footer: all copy moved to [[westgate:footer.*]] keys; year injected
  via filter:middleware.renderFooter instead of hard-coded 2026
- client.js: batch table measurements before writes (no interleaved
  reflow), .catch on the category class map so search results never
  hang, category selector match uses fw-bold class instead of inline
  style
- Forced-colors focus fallback: transparent outline alongside the
  box-shadow focus ring
- DESIGN.md: real radius scale (3/4/6/8px), code-block palette,
  motion & modes section, placeholder alpha

Verified against the sow-nodebb dev container: themed code blocks
render in posts, footer i18n + year, checkbox roles in served HTML.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scss/westgate/_surfaces.scss

@@ -141,7 +141,7 @@ samp,
 }
 
 .alert {
-  background: rgba(194, 163, 90, 0.08);
+  background: var(--wg-border-soft);
   border-color: rgba(194, 163, 90, 0.18);
   color: var(--wg-text-soft);
 }
@@ -291,7 +291,7 @@ li[component="category/topic"] .user-icon {
       rgba(8, 7, 10, 0.08)
     ),
     var(--wg-velvet-panel) !important;
-  border: 1px solid rgba(194, 163, 90, 0.14) !important;
+  border: 1px solid var(--wg-border) !important;
   border-radius: 8px !important;
   box-shadow:
     inset 0 1px 0 rgba(255, 244, 221, 0.028),
@@ -335,7 +335,7 @@ li[component="category/topic"] .user-icon {
 .chats-dropdown .mark-read:focus,
 .chats-list .mark-read:hover,
 .chats-list .mark-read:focus {
-  background: rgba(194, 163, 90, 0.08) !important;
+  background: var(--wg-border-soft) !important;
 }
 
 .chats-dropdown .chat-room-btn,
@@ -352,7 +352,7 @@ li[component="category/topic"] .user-icon {
 [component="chat/public/room"]:hover,
 [component="chat/public/room"]:focus,
 [component="chat/public/room"].unread {
-  background: rgba(194, 163, 90, 0.08) !important;
+  background: var(--wg-border-soft) !important;
   border-color: rgba(194, 163, 90, 0.24) !important;
   color: var(--wg-text) !important;
 }
@@ -387,7 +387,7 @@ li[component="category/topic"] .user-icon {
     rgba(216, 194, 138, 0.13),
     rgba(70, 45, 52, 0.28)
   ) !important;
-  border: 1px solid rgba(194, 163, 90, 0.28) !important;
+  border: 1px solid var(--wg-focus) !important;
   color: var(--wg-ledger-ink) !important;
 }