radio group: fix live validation after invalid

src/lib/RadioGroup.svelte

@@ -23,8 +23,20 @@
 		...props
 	}: Props = $props();
 	let valid = $state(true);
+	let hiddenInput: HTMLInputElement;
 
-	const group = new RadioGroup(props);
+	const group = new RadioGroup({
+		...props,
+		onValueChange(active) {
+			// call any passed in handler
+			props.onValueChange?.(active);
+
+			requestAnimationFrame(() => {
+				// send keyboard event to trigger validation
+				hiddenInput?.dispatchEvent(new KeyboardEvent('keyup'));
+			});
+		}
+	});
 	const isVert = $derived(group.orientation === 'vertical');
 </script>
 
@@ -69,8 +81,9 @@
 	</div>
 	<input
 		{...group.hiddenInput}
-		use:validate={{ required }}
+		use:validate={{ required, autovalOnInvalid: true }}
 		onvalidate={(e) => (valid = e.detail.valid)}
+		bind:this={hiddenInput}
 	/>
 
 	{#if required}