feat: port release-v2 experience improvements from PR #6582

Brings the semantically-correct unification work from the closed
agent/release-v2-experience PR into release/v2:

- universal create surface (header, board, spotlight) with permission-aware actions
- board empty state and setup checklist with widget/connection recipes
- in-widget integration editing via inspector modal, preserving unsaved widget settings
- single-source widget-integration capability map (nativeFeatureCapabilities)
- multi-endpoint Docker singleton with per-endpoint failure isolation, DOCKER_ENDPOINTS descriptors and service reconciliation
- Kubernetes multi-context registry with availability probing and context selector
- response-contract test harness and setup analytics property boundaries

Excludes the feature-platform generator/workbench tooling (deferred).

apps/nextjs/src/components/create/universal-create-modal.module.d.css.ts

@@ -0,0 +1,5 @@
+declare const classes: {
+  readonly action: string;
+  readonly actionIcon: string;
+};
+export default classes;