test(13-08): satisfy vue-tsc -b build-mode checks in test files

npm run build runs vue-tsc -b (project references, noUncheckedIndexedAccess),
stricter than the flat --noEmit used during Task 2 verification: indexed
CustomEvent accesses need non-null assertions, the suspended-chat Promise
needs an explicit <unknown> ctor, and one unused import. 41/41 still green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/composables/__tests__/archyContentAdapter.test.ts

@@ -2,7 +2,6 @@ import { describe, it, expect } from 'vitest'
 import {
   adaptContentItems,
   adaptToFilm,
-  adaptToSong,
   adaptToPodcast,
   classifyByMime,
   sortDeterministic,