chore(delegate-task): remove unused metadata model export

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/delegate-task/resolve-metadata-model.ts

@@ -1,6 +1,6 @@
 import type { DelegatedModelConfig } from "./types"
 
-export interface MetadataModel {
+interface MetadataModel {
   providerID: string
   modelID: string
   variant?: string