feat: use Vercel's deep-link for ai-gateway API key creation prompt

Vercel provides a d?to= redirect URL that routes users through their
team picker to the AI Gateway API keys management page. Using this
specific URL lands users directly on the "Create key" page instead of
the generic AI Gateway dashboard.

hermes_cli/main.py

@@ -2058,7 +2058,8 @@ def _model_flow_ai_gateway(config, current_model=""):
     api_key = get_env_value("AI_GATEWAY_API_KEY")
     if not api_key:
         print("No Vercel AI Gateway API key configured.")
-        print("Get one at: https://vercel.com/dashboard/ai-gateway")
+        print("Create API key here: https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai-gateway&title=AI+Gateway")
+        print("Add a payment method to get $5 in free credits.")
         print()
         try:
             import getpass