feat: rework percentile roll into a stateful tens+ones flow

Tens and Ones now combine into a real 1-100 percentile result
(00+0 = 100) instead of rolling independently. Ones is disabled
until Tens is rolled, and a pending visual state shows the tens
value while waiting for the ones roll. Adds a Clear button to
reset the flow.

public/css/styles.css

@@ -822,6 +822,14 @@ h1, h2, h3, h4, h5, h6 {
   line-height: 1;
 }
 
+.dice-result-box.pending {
+  border-color: var(--info);
+}
+
+.dice-total.pending-value {
+  color: var(--info);
+}
+
 .dice-breakdown {
   margin-top: 6px;
   font-family: var(--font-mono);