test(devtools): run the orphaned supported-apis spec

`supported-apis.spec.ts` was added in #60585, in a commit that also edited the
`ts_test_library` three lines below the `srcs` it was left out of. No revision
of that BUILD file has ever listed it, so it has not run since March 2025. The
target goes from 12 specs to 14.

Wiring it up alone would not have worked. Every `*IsSupported` helper calls
`ngDebugClient()`, which throws when `window.ng` is undefined, and the old
`expect(supported).toBeTruthy()` set no `ng` at all. It now stubs `ng` and
checks the flag set and that each flag tracks its own debug API.

`ng-debug-api.spec.ts` adds an `[ng-version]` root and did not remove it, which
`getAppRoots()` then picks up in the other file under jasmine's random
ordering, so it now clears the DOM in its own `afterEach`.

`glob` matches the sibling `directive-forest/component-tree` target and keeps
the next spec in this directory from being dropped the same way.

devtools/projects/ng-devtools-backend/src/lib/shared/ng-debug-api/BUILD.bazel

@@ -19,7 +19,7 @@ ng_project(
 
 ts_test_library(
     name = "ng-debug-api_test_lib",
-    srcs = ["ng-debug-api.spec.ts"],
+    srcs = glob(["*.spec.ts"]),
     deps = [
         ":ng-debug-api",
         "//:node_modules/@angular/core",

devtools/projects/ng-devtools-backend/src/lib/shared/ng-debug-api/ng-debug-api.spec.ts

@@ -61,6 +61,7 @@ const fakeNgGlobal = (framework: Framework): Partial<Ng> => {
 describe('ng-debug-api', () => {
   afterEach(() => {
     delete (globalThis as any).ng;
+    document.body.replaceChildren();
   });
 
   describe('ngDebugDependencyInjectionApiIsSupported', () => {

devtools/projects/ng-devtools-backend/src/lib/shared/ng-debug-api/supported-apis.spec.ts

@@ -9,11 +9,38 @@
 import {getSupportedApis} from './supported-apis';
 
 describe('supported-apis', () => {
+  afterEach(() => {
+    delete (globalThis as any).ng;
+  });
+
   describe('getSupportedApis', () => {
-    it('should return supported APIs', () => {
+    it('should return every flag as false when no debug API is available', () => {
+      (globalThis as any).ng = {};
+
       const supported = getSupportedApis();
 
-      expect(supported).toBeTruthy();
+      expect(Object.keys(supported).sort()).toEqual([
+        'dependencyInjection',
+        'profiler',
+        'routes',
+        'signalPropertiesInspection',
+        'signals',
+        'transferState',
+      ]);
+      expect(Object.values(supported).every((value) => value === false)).toBeTrue();
+    });
+
+    it('should only report signals when the signal graph API is available', () => {
+      (globalThis as any).ng = {ɵgetSignalGraph: () => {}};
+
+      const supported = getSupportedApis();
+
+      expect(supported.signals).toBeTrue();
+      expect(supported.dependencyInjection).toBeFalse();
+      expect(supported.profiler).toBeFalse();
+      expect(supported.routes).toBeFalse();
+      expect(supported.signalPropertiesInspection).toBeFalse();
+      expect(supported.transferState).toBeFalse();
     });
   });
 });