Add the Extrudex Design System v3 bundle

Tokens (light + dark, neumorphism, 54/54 WCAG AA contrast pairs), the
self-hosted JetBrains Mono fonts, and interactive mockups of every screen
across three iterations. Iteration 3 is final: phone, tablet and desktop
tiers, device preview, and "empty spool weight" terminology. The build
scripts regenerate the screens byte-identically from source.

Implementation is tracked in Maestro feature UI Refresh - V3.0
(224b72a1-8d84-4970-97ea-5dafa4d8ea3b).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

source/checks/contrast.py

@@ -0,0 +1,10 @@
+def lum(h):
+    h=h.lstrip('#'); r,g,b=[int(h[i:i+2],16)/255 for i in (0,2,4)]
+    f=lambda c: c/12.92 if c<=0.03928 else ((c+0.055)/1.055)**2.4
+    return 0.2126*f(r)+0.7152*f(g)+0.0722*f(b)
+def cr(a,b):
+    la,lb=sorted([lum(a),lum(b)],reverse=True); return (la+0.05)/(lb+0.05)
+import sys
+pairs=[l.split() for l in sys.stdin if l.strip()]
+for p in pairs:
+    print(f"{p[0]:>9} on {p[1]:>9}  {cr(p[0],p[1]):5.2f}  {' '.join(p[2:])}")