Keep helios/index out of the Node test runner.

amber/helpers requires helios/index only when Helios is opened, but
findNestedDependencies traces it, and the website does not depend on
Helios, so the build failed with ENOENT on helios/index.js.

It is stubbed empty and excluded, as amber's own test runner does.

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

Gruntfile.js

@@ -92,6 +92,7 @@ module.exports = function (grunt) {
                     rawText: {
                         "jquery": "/* do not load in node test runner */",
                         "amber/legacy/IDE": "/* do not load in node test runner */",
+                        "helios/index": "",
                         "__app__": "(" + function () {
                             define(["testing", "amber/core/Platform-Node", "amber_devkit/NodeTestRunner"], function (amber) {
                                 amber.initialize().then(function () {
@@ -107,6 +108,7 @@ module.exports = function (grunt) {
                     },
                     include: ['app'],
                     findNestedDependencies: true,
+                    exclude: ['helios/index'],
                     insertRequire: ['app'],
                     optimize: "none",
                     wrap: helpers.nodeWrapperWithShebang,