refactor: move provider model helpers into plugins

extensions/byteplus/api.ts

@@ -1 +1,8 @@
 export { buildBytePlusCodingProvider, buildBytePlusProvider } from "./provider-catalog.js";
+export {
+  buildBytePlusModelDefinition,
+  BYTEPLUS_BASE_URL,
+  BYTEPLUS_CODING_BASE_URL,
+  BYTEPLUS_CODING_MODEL_CATALOG,
+  BYTEPLUS_MODEL_CATALOG,
+} from "./models.js";