fix(@angular/cli): improve error message extraction for unfetchable packages

Use instanceof check and optional chaining fallback to properly
extract error messages from Error instances and plain objects.

Author: maruthang

packages/angular/cli/src/commands/update/schematic/index.ts

@@ -858,7 +858,7 @@ export default function (options: UpdateSchema): Rule {
           // If the package cannot be fetched (e.g. private registry, JSR, AWS CodeArtifact,
           // or local workspace packages), return a partial object so the reduce below can
           // decide whether to warn or hard-fail based on whether it was explicitly requested.
-          const message = (error as { message?: string }).message ?? String(error);
+          const message = error instanceof Error ? error.message : (error as any)?.message ?? String(error);
           logger.warn(
             `Package '${depName}' could not be fetched from the registry: ${message}`,
           );