Item cards: no paragraph margin under the description

`.item-card` is a grid with a 0.4rem gap; the global `p` bottom
margin (0.9em) stacked on top of it under every description.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01L4jrCgLiKKHAEFuZUJjckH

style/main.css

@@ -1045,6 +1045,9 @@ textarea:focus {
 .item-card-description {
   font-size: 0.9rem;
   color: var(--ink-dim);
+  /* The card is a grid with its own gap; the global p bottom margin
+     would stack on top of it. */
+  margin: 0;
 }
 
 .item-card-fields {