test: lotus decorations, call caps, crypto, featureCheck, typing, markdown (+34)

Subagent batch (no bugs found) + markdown:
- lotus/avatarDecorations (8): decorationUrl, CDN shape, ALL_DECORATIONS
  flattening, data invariants (unique category ids + slugs, slug charset).
- plugins/call/utils (7): getCallCapabilities — static caps + room/user/device
  scoped state-keys.
- utils/matrix-crypto (3): verifiedDevice via a stubbed CryptoApi.
- utils/featureCheck (3): checkIndexedDBSupport success/error/throw paths.
- state/typingMembers (8): add/dedup-by-latest-ts/per-room-scope/delete reducer
  via a jotai store (enableMapSet, mirroring app startup).
- plugins/markdown/utils (5): inline + block escape/unescape round-trips.

Full suite now 231 tests, all passing.

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

src/app/utils/featureCheck.test.ts

@@ -0,0 +1,63 @@
+import { test, afterEach } from 'node:test';
+import assert from 'node:assert/strict';
+import { checkIndexedDBSupport } from './featureCheck';
+
+// `checkIndexedDBSupport` resolves by talking to the global `indexedDB`. There
+// is no real IndexedDB in this Node test environment, so each case installs a
+// minimal stub on `globalThis.indexedDB` and restores it afterwards.
+type OpenRequest = {
+  onsuccess?: () => void;
+  onerror?: () => void;
+};
+
+const originalIndexedDB = (globalThis as { indexedDB?: unknown }).indexedDB;
+
+afterEach(() => {
+  (globalThis as { indexedDB?: unknown }).indexedDB = originalIndexedDB;
+});
+
+const installIndexedDB = (impl: unknown) => {
+  (globalThis as { indexedDB?: unknown }).indexedDB = impl;
+};
+
+test('resolves true when the open request fires onsuccess', async () => {
+  let deleted = false;
+  installIndexedDB({
+    open: (): OpenRequest => {
+      const req: OpenRequest = {};
+      // fire async, mimicking the real event loop
+      queueMicrotask(() => req.onsuccess?.());
+      return req;
+    },
+    deleteDatabase: () => {
+      deleted = true;
+    },
+  });
+
+  assert.equal(await checkIndexedDBSupport(), true);
+  assert.equal(deleted, true);
+});
+
+test('resolves false when the open request fires onerror', async () => {
+  installIndexedDB({
+    open: (): OpenRequest => {
+      const req: OpenRequest = {};
+      queueMicrotask(() => req.onerror?.());
+      return req;
+    },
+    deleteDatabase: () => {},
+  });
+
+  assert.equal(await checkIndexedDBSupport(), false);
+});
+
+test('resolves false when indexedDB.open throws synchronously', async () => {
+  installIndexedDB({
+    open: () => {
+      throw new Error('blocked');
+    },
+    deleteDatabase: () => {},
+  });
+
+  assert.equal(await checkIndexedDBSupport(), false);
+});