refactor(#248): extract typeahead logic into createTypeahead composable, use in PersonTypeahead

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/hooks/useTypeahead.svelte.ts

@@ -41,6 +41,12 @@ export function createTypeahead<T>(options: Options<T>) {
 		close();
 	}
 
+	/** Directly populate results without going through the debounce (e.g. on-focus preload). */
+	function openWith(items: T[]) {
+		results = items;
+		isOpen = true;
+	}
+
 	return {
 		get query() {
 			return query;
@@ -59,6 +65,7 @@ export function createTypeahead<T>(options: Options<T>) {
 		},
 		setQuery,
 		close,
-		select
+		select,
+		openWith
 	};
 }