Updated the files.

my-app/node_modules/@angular-devkit/schematics/tasks/run-schematic/executor.d.ts

@@ -0,0 +1,10 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+import { TaskExecutor } from '../../src';
+import { RunSchematicTaskOptions } from './options';
+export default function (): TaskExecutor<RunSchematicTaskOptions<{}>>;

my-app/node_modules/@angular-devkit/schematics/tasks/run-schematic/executor.js

@@ -0,0 +1,29 @@
+"use strict";
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+Object.defineProperty(exports, "__esModule", { value: true });
+function default_1() {
+    return (options, context) => {
+        if (!options?.name) {
+            throw new Error('RunSchematicTask requires an options object with a non-empty name property.');
+        }
+        const maybeWorkflow = context.engine.workflow;
+        const collection = options.collection || context.schematic.collection.description.name;
+        if (!maybeWorkflow) {
+            throw new Error('Need Workflow to support executing schematics as post tasks.');
+        }
+        return maybeWorkflow.execute({
+            collection: collection,
+            schematic: options.name,
+            options: options.options,
+            // Allow private when calling from the same collection.
+            allowPrivate: collection == context.schematic.collection.description.name,
+        });
+    };
+}
+exports.default = default_1;

my-app/node_modules/@angular-devkit/schematics/tasks/run-schematic/options.d.ts

@@ -0,0 +1,13 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+export declare const RunSchematicName = "run-schematic";
+export interface RunSchematicTaskOptions<T> {
+    collection: string | null;
+    name: string;
+    options: T;
+}

my-app/node_modules/@angular-devkit/schematics/tasks/run-schematic/options.js

@@ -0,0 +1,11 @@
+"use strict";
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.RunSchematicName = void 0;
+exports.RunSchematicName = 'run-schematic';

my-app/node_modules/@angular-devkit/schematics/tasks/run-schematic/task.d.ts

@@ -0,0 +1,17 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+import { TaskConfiguration, TaskConfigurationGenerator } from '../../src';
+import { RunSchematicTaskOptions } from './options';
+export declare class RunSchematicTask<T> implements TaskConfigurationGenerator<RunSchematicTaskOptions<T>> {
+    protected _collection: string | null;
+    protected _schematic: string;
+    protected _options: T;
+    constructor(s: string, o: T);
+    constructor(c: string, s: string, o: T);
+    toConfiguration(): TaskConfiguration<RunSchematicTaskOptions<T>>;
+}

my-app/node_modules/@angular-devkit/schematics/tasks/run-schematic/task.js

@@ -0,0 +1,37 @@
+"use strict";
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.RunSchematicTask = void 0;
+const options_1 = require("./options");
+class RunSchematicTask {
+    _collection;
+    _schematic;
+    _options;
+    constructor(c, s, o) {
+        if (arguments.length == 2 || typeof s !== 'string') {
+            o = s;
+            s = c;
+            c = null;
+        }
+        this._collection = c;
+        this._schematic = s;
+        this._options = o;
+    }
+    toConfiguration() {
+        return {
+            name: options_1.RunSchematicName,
+            options: {
+                collection: this._collection,
+                name: this._schematic,
+                options: this._options,
+            },
+        };
+    }
+}
+exports.RunSchematicTask = RunSchematicTask;