Count the Sound FX type in the + menu check

The suite run on 183f356 (task 507) failed three checks of e2e 04.
They compare the + menu with a fixed count of asset types, and the
Sound FX type from de14f0f made it 27 instead of 26.

- ASSET_TYPE_COUNT in e2e 04 is now 27. The menu itself was right:
  the log lists every type once, sorted, with Sound FX in the library.

Tests:
- e2e 04 (melektaus-atx): ALL PASSED - 62 checks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/e2e/04-assets.mjs

@@ -2,7 +2,7 @@ import { colourDistance } from '../lib/harness.mjs';
 import { inView } from './lib/scaffold.mjs';
 
 /** One per entry of `ASSET_TYPES` – a new asset type counts here too. */
-const ASSET_TYPE_COUNT = 26;
+const ASSET_TYPE_COUNT = 27;
 
 /** The asset panel: placing by dragging into the view, creating through "+", and resetting an asset value. */
 export async function assets(t) {