feat(m4): verify signed surface bundles across hosts

tauri/src/runtime/surface-registry.ts

@@ -48,6 +48,12 @@ export type SurfaceOpenRequest = Readonly<{
   state?: JsonObject;
 }>;
 
+/** Shared contract for development and production Surface admission policies. */
+export interface SurfaceAdmissionPolicy {
+  validateOpenRequest(payload: unknown): SurfaceRegistryResult;
+  validateState(appID: string, version: string, state: unknown): SurfaceRegistryResult;
+}
+
 const APP_ID = /^[a-z][a-z0-9]*(?:[.-][a-z0-9]+)*$/;
 const VERSION = /^\d+\.\d+\.\d+(?:-[0-9A-Za-z.-]+)?(?:\+[0-9A-Za-z.-]+)?$/;
 const BUNDLE_ID = /^[a-z][a-z0-9]*(?:[._-][a-z0-9]+)*$/;