Fix front artwork gap at right bleed edge

Image was sized to trim-w (8.5 in) but the zone is trim-w + bleed
(8.625 in), leaving a 0.125 in uncovered strip. width/height 100%
fills the full zone, matching how back-artwork is sized.

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

templates/cover.html

@@ -255,10 +255,9 @@
     /* ── Front cover content ────────────────────────────────── */
     .front-artwork {
       position: absolute;
-      /* art fills from left trim edge (skip the right bleed) */
       top: 0; left: 0;
-      width: var(--trim-w);
+      width: 100%;
-      height: var(--total-h);
+      height: 100%;
       object-fit: cover;
     }