docs(search): explain void sort/dir ESLint workaround in SearchFilterBar

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

frontend/src/routes/SearchFilterBar.svelte

@@ -45,7 +45,8 @@ let {
 let sortDirMounted = false;
 
 $effect(() => {
-	// Track sort and dir so this effect re-runs when either changes
+	// Read sort and dir so Svelte tracks them as dependencies of this effect.
+	// `void` suppresses the ESLint no-unused-expressions rule for bare variable reads.
 	void sort;
 	void dir;
 	if (!sortDirMounted) {