Add sort toggle for discussions (activity / newest)

src/lib/sort.svelte.ts

@@ -0,0 +1,22 @@
+import { browser } from "$app/environment";
+import type { SortMode } from "$lib/threads.svelte";
+
+const KEY = "squalk:sort";
+
+function read(): SortMode {
+  if (!browser) return "active";
+  return localStorage.getItem(KEY) === "new" ? "new" : "active";
+}
+
+let pref = $state<SortMode>(read());
+
+// Global, remembered across home and rooms; survives reloads.
+export const sortPref = {
+  get value() {
+    return pref;
+  },
+  set value(v: SortMode) {
+    pref = v;
+    if (browser) localStorage.setItem(KEY, v);
+  },
+};