combobox: use popover attachment to manage positioning

src/routes/+page.svelte

@@ -184,7 +184,7 @@
 			]}
 			onchange={(e) => console.log('Selected:', e.value)}
 			onvalidate={(e) => console.log('Validation:', e.detail)}
-			pickerWidth="max-match"
+			pickerWidth="longest"
 		>
 			{#snippet labelRender(opt: ComboboxOption)}
 				Processed {opt.label}