feat(grok-cli): add Grok CLI / Grok Build provider with OAuth device-code flow (#2502)

New OAuth provider routing through cli-chat-proxy.grok.com (OpenAI Responses
API), distinct from xai (api.x.ai) and grok-web (cookie SSO):

- Registry + GrokCliExecutor: Chat Completions -> Responses transform, CLI
  fingerprint headers, virtual effort models grok-4.5-{low,medium,high}
- OAuth device-code flow (auth.x.ai) with no-PKCE, shared xAI token refresh
- store=false multi-turn continuity via reasoning encrypted_content
- Quota tracker: on-demand window + prepaid balance on dashboard
- Connection test: 402 spending-limit = soft success (auth OK, out of credits)
- Alias/oauth/provider baselines + unit tests

package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "dev": "next dev --webpack --port 20127",
     "build": "next build --webpack",
-    "start": "next start",
+    "start": "next start --port 20127",
     "dev:bun": "bun --bun next dev --webpack --port 20127",
     "build:bun": "bun --bun next build --webpack",
     "start:bun": "bun ./.next/standalone/server.js",