arch(sprint1): add unknown widget fallback diagnostics

src/app/core/runtime/runtime-diagnostics.service.ts

@@ -0,0 +1,16 @@
+import { Injectable } from '@angular/core';
+
+export interface UnknownWidgetDiagnostic {
+  tenant: string;
+  page: string;
+  section: string;
+  widget: string;
+  reason: string;
+}
+
+@Injectable({ providedIn: 'root' })
+export class RuntimeDiagnosticsService {
+  logUnknownWidget(event: UnknownWidgetDiagnostic): void {
+    console.warn('[PlatformRuntime][UnknownWidget]', event);
+  }
+}