Fix front-overlay not covering right bleed edge

Overlay was sized to var(--trim-w) like the old artwork, leaving the
right 0.125 in strip of the zone undarked. Changed to width/height 100%.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/cover.html

@@ -265,8 +265,8 @@
     .front-overlay {
       position: absolute;
       top: 0; left: 0;
-      width: var(--trim-w);
-      height: var(--total-h);
+      width: 100%;
+      height: 100%;
       background:
         /* deep vignette around all edges */
         radial-gradient(ellipse 90% 90% at 50% 50%,