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/web/server/lib/quota/routes.js

@@ -1,11 +1,9 @@
 import express from 'express';
 import { deleteManagedCredential, getManagedCredentialStatus, normalizers, readManagedCredential, writeManagedCredential } from './credentials/providers.js';
-import { fetchOpenCodeGoUsage } from './providers/opencode-go.js';
 import { fetchOllamaCloudUsage } from './providers/ollama-cloud.js';
 import { importCursorCredential, validateCursorCredential } from './providers/cursor.js';
 
 const validators = {
-  'opencode-go': fetchOpenCodeGoUsage,
   'ollama-cloud': fetchOllamaCloudUsage,
   cursor: validateCursorCredential,
 };