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/backupRestore.test.ts

@@ -0,0 +1,68 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { createStore } from 'jotai';
+import { ImportRoomKeyProgressData, ImportRoomKeyStage } from 'matrix-js-sdk/lib/crypto-api';
+import { backupRestoreProgressAtom, BackupProgressStatus } from './backupRestore';
+
+// backupRestoreProgressAtom maps ImportRoomKeyProgressData stages onto an
+// IBackupProgress status held in an unexported baseAtom:
+//   Fetch    -> Fetching
+//   LoadKeys with successes+failures === total -> Done
+//   LoadKeys otherwise -> Loading{ downloaded = successes+failures }
+// We drive the write atom through a jotai store and read back the getter.
+
+const load = (successes: number, failures: number, total: number): ImportRoomKeyProgressData => ({
+  stage: ImportRoomKeyStage.LoadKeys,
+  successes,
+  failures,
+  total,
+});
+
+test('starts Idle', () => {
+  const store = createStore();
+  assert.deepEqual(store.get(backupRestoreProgressAtom), {
+    status: BackupProgressStatus.Idle,
+  });
+});
+
+test('Fetch stage -> Fetching', () => {
+  const store = createStore();
+  store.set(backupRestoreProgressAtom, { stage: ImportRoomKeyStage.Fetch });
+  assert.deepEqual(store.get(backupRestoreProgressAtom), {
+    status: BackupProgressStatus.Fetching,
+  });
+});
+
+test('LoadKeys with downloaded === total -> Done', () => {
+  const store = createStore();
+  store.set(backupRestoreProgressAtom, load(8, 2, 10));
+  assert.deepEqual(store.get(backupRestoreProgressAtom), {
+    status: BackupProgressStatus.Done,
+  });
+});
+
+test('LoadKeys mid-progress -> Loading with downloaded = successes + failures', () => {
+  const store = createStore();
+  store.set(backupRestoreProgressAtom, load(3, 1, 10));
+  assert.deepEqual(store.get(backupRestoreProgressAtom), {
+    status: BackupProgressStatus.Loading,
+    data: { downloaded: 4, successes: 3, failures: 1, total: 10 },
+  });
+});
+
+test('LoadKeys at zero progress -> Loading with downloaded 0', () => {
+  const store = createStore();
+  store.set(backupRestoreProgressAtom, load(0, 0, 5));
+  assert.deepEqual(store.get(backupRestoreProgressAtom), {
+    status: BackupProgressStatus.Loading,
+    data: { downloaded: 0, successes: 0, failures: 0, total: 5 },
+  });
+});
+
+test('Fetch then LoadKeys completion transitions Fetching -> Done', () => {
+  const store = createStore();
+  store.set(backupRestoreProgressAtom, { stage: ImportRoomKeyStage.Fetch });
+  assert.equal(store.get(backupRestoreProgressAtom).status, BackupProgressStatus.Fetching);
+  store.set(backupRestoreProgressAtom, load(5, 0, 5));
+  assert.equal(store.get(backupRestoreProgressAtom).status, BackupProgressStatus.Done);
+});