Route a free NVIDIA key through one URL

A raw NVIDIA key only works in NVIDIA's client. Other apps still need their own keys, and you get no failover if NIM is down.

1. 1.Create a free NVIDIA API key from NVIDIA's developer site.
2. 2.Add it under BYOK in the AnyRouter dashboard.
3. 3.Call AnyRouter with your sk-ar key. Use anyrouter/free when you want the shared free chain instead of one provider.

curl https://anyrouter.dev/api/v1/chat/completions \
  -H "Authorization: Bearer $ANYROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anyrouter/free",
    "messages": [{ "role": "user", "content": "Say hello in one sentence." }]
  }'