Support idle primary device warning alert from server

ts/test-both/util/serverAlerts_test.ts

@@ -0,0 +1,45 @@
+// Copyright 2025 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+import {
+  getServerAlertToShow,
+  ServerAlert,
+} from '../../util/handleServerAlerts';
+import { DAY, MONTH, WEEK } from '../../util/durations';
+
+describe('serverAlerts', () => {
+  it('should prefer critical alerts', () => {
+    assert.strictEqual(
+      getServerAlertToShow({
+        [ServerAlert.CRITICAL_IDLE_PRIMARY_DEVICE]: {
+          firstReceivedAt: Date.now(),
+        },
+        [ServerAlert.IDLE_PRIMARY_DEVICE]: { firstReceivedAt: Date.now() },
+      }),
+      ServerAlert.CRITICAL_IDLE_PRIMARY_DEVICE
+    );
+  });
+  it('should not show idle device warning if dismissed < 1 week', () => {
+    assert.strictEqual(
+      getServerAlertToShow({
+        [ServerAlert.IDLE_PRIMARY_DEVICE]: {
+          firstReceivedAt: Date.now() - MONTH,
+          dismissedAt: Date.now() - DAY,
+        },
+      }),
+      null
+    );
+  });
+  it('should show idle device warning if dismissed > 1 week', () => {
+    assert.strictEqual(
+      getServerAlertToShow({
+        [ServerAlert.IDLE_PRIMARY_DEVICE]: {
+          firstReceivedAt: Date.now() - MONTH,
+          dismissedAt: Date.now() - WEEK - 1,
+        },
+      }),
+      ServerAlert.IDLE_PRIMARY_DEVICE
+    );
+  });
+});