dist: Address Copilot review suggestions from PR #1042 (GraalVM Community) (#1059)

- installer: surface a clear error when the GraalVM Community releases
  listing is not a JSON array, instead of silently treating an error
  payload (rate limit, auth failure, etc.) as "no releases" which later
  surfaced as a misleading "version not found" error.
- docs: fix the GraalVM Community advanced-usage example to check the
  installed binary versions (java/native-image --version) rather than
  running a non-existent HelloWorldApp classpath that fails when copied.
- tests: cover the new non-array release listing error path.

Rebuilt dist bundle.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

__tests__/distributors/graalvm-installer.test.ts

@@ -1058,6 +1058,20 @@ describe('GraalVMDistribution', () => {
           'GraalVM Community does not provide early access builds'
         );
       });
+
+      it('should surface an error when the releases listing is not an array', async () => {
+        mockHttpClient.getJson.mockResolvedValue({
+          result: {message: 'API rate limit exceeded'},
+          statusCode: 403,
+          headers: {}
+        });
+
+        await expect(
+          (communityDistribution as any).findPackageForDownload('21')
+        ).rejects.toThrow(
+          /Unexpected response while listing GraalVM Community releases.*HTTP status code: 403/s
+        );
+      });
     });
   });
 });