test(cli): the verify host-root fixture main added declares the current protocol, ^18

#22381 (97610a5) added test/verify-host-root.test.ts with a current-app
fixture pinned to engines.protocol '^17'. Under PROTOCOL_VERSION 18.0.0 the
runtime handshake refuses that app, so `os verify` exits 1 before the pin's
subject (the app-dir anchoring) is ever reached. The fixture now declares
'^18', the same sweep rule this branch applies to every current-app fixture.

Claude-Session: https://claude.ai/code/session_01VZqqwTj2wsihZEbfT6yyYN
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

packages/cli/test/verify-host-root.test.ts

@@ -53,7 +53,7 @@ const STACK = {
     version: '1.0.0',
     name: 'Verify Host Root',
     type: 'app',
-    engines: { protocol: '^17' },
+    engines: { protocol: '^18' },
   },
   objects: [
     {