feat(03-03): add OpenRouter, LiteLLM, Cloudflare, Vercel, Portkey, Helicone gateways

- sk-or-v1- and sk-helicone- high-confidence prefix regex
- LiteLLM low-confidence sk- pattern with master key keyword
- Cloudflare, Vercel, Portkey keyword-anchored detection

pkg/providers/definitions/vercel-ai.yaml

@@ -0,0 +1,17 @@
+format_version: 1
+name: vercel-ai
+display_name: Vercel AI Gateway
+tier: 5
+last_verified: "2026-04-05"
+keywords:
+  - "vercel"
+  - "VERCEL_AI_GATEWAY"
+  - "AI_GATEWAY_API_KEY"
+  - "vercel.ai"
+  - "ai-sdk"
+verify:
+  method: GET
+  url: ""
+  headers: {}
+  valid_status: []
+  invalid_status: []