feat(adapters): declarative config-schema API and UI for plugin adapters

Cherry-picked from feat/externalize-hermes-adapter.
Resolved conflicts: kept Hermes as built-in on phase1 branch.

server/src/adapters/types.ts

@@ -25,5 +25,8 @@ export type {
   NativeContextManagement,
   ResolvedSessionCompactionPolicy,
   SessionCompactionPolicy,
+  ConfigFieldOption,
+  ConfigFieldSchema,
+  AdapterConfigSchema,
   ServerAdapterModule,
 } from "@paperclipai/adapter-utils";