feat: switch OpenCode Go usage to API

OpenCode Go now reads quota usage with a bearer API key from OpenCode auth.json
Removes the old workspace ID and browser cookie credential flow
Deletes legacy OpenCode Go credential files during upgrade

packages/vscode/webview/main.tsx

@@ -1064,7 +1064,7 @@ const handleLocalApiRequest = async (input: RequestInfo | URL, url: URL, init: R
     }
   }
 
-  const quotaCredentialMatch = pathname.match(/^\/api\/quota\/credentials\/(opencode-go|ollama-cloud|cursor)(?:\/(validate|import))?$/);
+  const quotaCredentialMatch = pathname.match(/^\/api\/quota\/credentials\/(ollama-cloud|cursor)(?:\/(validate|import))?$/);
   if (quotaCredentialMatch) {
     try {
       const body = method === 'PUT' ? await extractJsonBody(input, init, method) : undefined;