Feat v0.6.14 visual polish

Fix v0.6.13 spacing regressions with half-step tokens (--sp-1h 6px,
--sp-2h 10px). Purge ~65 stale hex/rgba fallback values from var() calls
including all old gold #b38a4e references. Self-host DM Sans and JetBrains
Mono woff2 fonts, eliminating Google Fonts CDN dependency. Standardize
border-radius to three tokens (--radius-sm 4px, --radius 8px, --radius-lg
12px) across all kernel CSS and 12 extension packages.

Also fixes: theme settings showing resolved mode instead of stored preference,
surface-inner overflow causing notes scrollbar and chat input clipping at
high zoom, user menu drift at scale >100% from zoom-unaware fixed positioning,
and three undefined CSS variable references.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/pages/templates/base.html

@@ -29,7 +29,7 @@
     <style>
         body { margin: 0; background: var(--bg); color: var(--text); display: flex; flex-direction: column; height: 100vh; height: 100dvh; overflow: hidden; padding: env(safe-area-inset-top, 0) env(safe-area-inset-right, 0) env(safe-area-inset-bottom, 0) env(safe-area-inset-left, 0); }
         .surface { flex: 1; min-height: 0; overflow: hidden; }
-        .surface-inner { width: 100%; height: 100%; }
+        .surface-inner { width: 100%; height: 100%; overflow: hidden; }
         .banner { flex-shrink: 0; }
     </style>
     <meta name="theme-color" content="#0e0e10" id="metaThemeColor">