render side art as stacked per-color layers (fixes torn right panel, much lighter layout)

css/style.css

@@ -213,12 +213,13 @@ button {
   pointer-events: none;
   user-select: none;
 }
-.side i { font-style: normal; }
+/* the art comes as one layer per color, stacked */
+.side { display: grid; }
+.side > span { grid-area: 1 / 1; direction: ltr; unicode-bidi: isolate; }
 .side-left { left: 0; }
-/* rtl only so the right panel clips on its inner edge; the art itself stays
-   ltr, or the bidi algorithm reorders runs of punctuation */
+/* rtl only so the right panel clips on its inner edge; the layers stay ltr
+   (above), or the bidi algorithm reorders runs of punctuation */
 .side-right { right: 0; direction: rtl; }
-.side-right > span { direction: ltr; unicode-bidi: isolate; }
 
 /* the column's shadow: the art fades out under it instead of stopping dead
    beside the text. Eased falloff, as wide as about a third of the margin. */