fix(a11y): opening a filter list from the keyboard moves focus to its options (#33025)

src/lib/components/common/Select.svelte

@@ -105,11 +105,21 @@
 		}
 	}
 
-	async function toggleOpen() {
+	async function toggleOpen(focusContent = false) {
 		open = !open;
 		if (open) {
 			await tick();
 			positionContent();
+			if (focusContent) {
+				contentEl?.querySelector<HTMLElement>('button:not([disabled]), a[href], input')?.focus();
+			}
+		}
+	}
+
+	function handleTriggerKeydown(event) {
+		if (event.target === triggerEl && (event.key === 'Enter' || event.key === ' ')) {
+			event.preventDefault();
+			toggleOpen(true);
 		}
 	}
 
@@ -123,15 +133,19 @@
 
 	function handleKeydown(event) {
 		if (event.key === 'Escape' && open) {
+			const restoreFocus = contentEl?.contains(document.activeElement);
 			open = false;
 			onClose();
+			if (restoreFocus) triggerEl?.focus();
 		}
 	}
 
 	export function selectItem(item) {
+		const restoreFocus = contentEl?.contains(document.activeElement);
 		value = item.value;
 		open = false;
 		onChange(value);
+		if (restoreFocus) triggerEl?.focus();
 	}
 </script>
 
@@ -147,7 +161,8 @@
 	class="focus-ring {triggerClass}"
 	type="button"
 	aria-expanded={open}
-	on:click={toggleOpen}
+	on:click={() => toggleOpen()}
+	on:keydown={handleTriggerKeydown}
 >
 	<slot name="trigger" {selectedLabel} {open}>
 		<span class={labelClass}>