Add HostContract interface per design spec §2.4

src/host-contract.ts

@@ -0,0 +1,20 @@
+import type { Logger } from "@/observability/logger/types";
+
+/**
+ * Contract a host application must implement to embed this component
+ * as an MF 2.0 remote. Both standalone SSR and remote modes satisfy
+ * this interface; features depend only on HostContract and never on
+ * the hosting mode.
+ */
+export interface HostContract {
+  /** Resolved locale, e.g. "ru", "en". */
+  locale: string;
+  /** Canonical origin for SEO (e.g. "https://flights.aeroflot.ru"). */
+  canonicalOrigin: string;
+  /** Optional deep-link navigation override from the host router. */
+  navigate?: (path: string) => void;
+  /** Optional consent flags; absent == assumed true. */
+  consent?: { analytics: boolean; telemetry: boolean };
+  /** Optional host logger for log stream merging. */
+  logger?: Logger;
+}