test: add suites for 8 simple state reducers + msgContent (+50)

Via subagent, all verified, no bugs:
- state/toast (7), room-list/roomList (6), inviteList (6), room-list/utils
  compareRoomsEqual (6), backupRestore (6), callEmbed dispose-on-replace (6),
  closedNavCategories factory + makeNavCategoryId (8).
- features/room/msgContent (5): getAudioMsgContent/getFileMsgContent incl.
  encrypted (content.file) vs plain (content.url) branch.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/state/closedNavCategories.test.ts

@@ -0,0 +1,104 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { createStore } from 'jotai';
+import { enableMapSet } from 'immer';
+import { makeClosedNavCategoriesAtom, makeNavCategoryId } from './closedNavCategories';
+
+// makeClosedNavCategoriesAtom(userId) builds a Set<string> atom whose reducer uses
+// immer produce (PUT add / DELETE delete) and persists to a per-user localStorage
+// key `closedNavCategories<userId>`. The reducers produce over a Set, so we enable
+// immer's Map/Set plugin (the app does this once at startup).
+// makeNavCategoryId joins args with '|'.
+enableMapSet();
+
+// In-memory localStorage so atomWithLocalStorage can read/write at construction
+// and on set. window is referenced for the onMount storage listener.
+type Store = Record<string, string>;
+const installLocalStorage = (): Store => {
+  const data: Store = {};
+  const ls = {
+    getItem: (k: string) => (k in data ? data[k] : null),
+    setItem: (k: string, v: string) => {
+      data[k] = String(v);
+    },
+    removeItem: (k: string) => {
+      delete data[k];
+    },
+  };
+  (globalThis as { localStorage?: unknown }).localStorage = ls;
+  (globalThis as { window?: unknown }).window = {
+    addEventListener: () => undefined,
+    removeEventListener: () => undefined,
+  };
+  return data;
+};
+
+test('makeNavCategoryId joins args with "|"', () => {
+  assert.equal(makeNavCategoryId('a', 'b', 'c'), 'a|b|c');
+  assert.equal(makeNavCategoryId('only'), 'only');
+  assert.equal(makeNavCategoryId(), '');
+});
+
+test('starts empty when nothing is stored', () => {
+  installLocalStorage();
+  const store = createStore();
+  const navAtom = makeClosedNavCategoriesAtom('@u:server');
+  assert.equal(store.get(navAtom).size, 0);
+});
+
+test('hydrates the Set from the per-user localStorage key', () => {
+  const data = installLocalStorage();
+  data['closedNavCategories@u:server'] = JSON.stringify(['x', 'y']);
+  const store = createStore();
+  const navAtom = makeClosedNavCategoriesAtom('@u:server');
+  assert.deepEqual(Array.from(store.get(navAtom)).sort(), ['x', 'y']);
+});
+
+test('PUT adds a category and DELETE removes it', () => {
+  installLocalStorage();
+  const store = createStore();
+  const navAtom = makeClosedNavCategoriesAtom('@u:server');
+
+  store.set(navAtom, { type: 'PUT', categoryId: 'cat1' });
+  assert.deepEqual(Array.from(store.get(navAtom)), ['cat1']);
+
+  store.set(navAtom, { type: 'DELETE', categoryId: 'cat1' });
+  assert.equal(store.get(navAtom).has('cat1'), false);
+});
+
+test('PUT of an existing category keeps the Set unchanged (idempotent)', () => {
+  installLocalStorage();
+  const store = createStore();
+  const navAtom = makeClosedNavCategoriesAtom('@u:server');
+  store.set(navAtom, { type: 'PUT', categoryId: 'cat1' });
+  store.set(navAtom, { type: 'PUT', categoryId: 'cat1' });
+  assert.equal(store.get(navAtom).size, 1);
+});
+
+test('DELETE of an absent category is a no-op', () => {
+  installLocalStorage();
+  const store = createStore();
+  const navAtom = makeClosedNavCategoriesAtom('@u:server');
+  store.set(navAtom, { type: 'DELETE', categoryId: 'missing' });
+  assert.equal(store.get(navAtom).size, 0);
+});
+
+test('writes persist to localStorage as an array', () => {
+  const data = installLocalStorage();
+  const store = createStore();
+  const navAtom = makeClosedNavCategoriesAtom('@u:server');
+  store.set(navAtom, { type: 'PUT', categoryId: 'cat1' });
+  assert.deepEqual(JSON.parse(data['closedNavCategories@u:server']), ['cat1']);
+});
+
+test('the storage key is namespaced per user', () => {
+  const data = installLocalStorage();
+  const store = createStore();
+  const aAtom = makeClosedNavCategoriesAtom('@a:server');
+  const bAtom = makeClosedNavCategoriesAtom('@b:server');
+
+  store.set(aAtom, { type: 'PUT', categoryId: 'only-a' });
+  assert.deepEqual(JSON.parse(data['closedNavCategories@a:server']), ['only-a']);
+  assert.equal(data['closedNavCategories@b:server'], undefined);
+  assert.equal(store.get(bAtom).size, 0);
+});