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>

packages/tasks/css/main.css

@@ -117,7 +117,7 @@
 .ext-tasks-card__status {
   font-size: 11px;
   padding: 2px var(--sp-2);
-  border-radius: 10px;
+  border-radius: var(--radius-lg);
   font-weight: 500;
 }
 .ext-tasks-card__status--todo        { background: var(--accent-dim); color: var(--accent); }
@@ -196,7 +196,7 @@
   color: var(--text-3);
   background: var(--bg-hover);
   padding: 1px 7px;
-  border-radius: 10px;
+  border-radius: var(--radius-lg);
 }
 .ext-tasks-board__col-body {
   flex: 1;