feat(02-03): add Together, Fireworks, Baseten, DeepInfra provider YAMLs

- Together AI: keyword-anchored, 64-hex generic pattern
- Fireworks AI: fw_ prefix (medium) + generic (low)
- Baseten: keyword + Api-Key header auth
- DeepInfra: keyword-anchored generic pattern
- Dual-located in providers/ and pkg/providers/definitions/

providers/baseten.yaml

@@ -0,0 +1,21 @@
+format_version: 1
+name: baseten
+display_name: Baseten
+tier: 2
+last_verified: "2026-04-05"
+keywords:
+  - "baseten"
+  - "BASETEN_API_KEY"
+  - "api.baseten.co"
+  - "Api-Key"
+patterns:
+  - regex: '[A-Za-z0-9]{40,}'
+    entropy_min: 4.0
+    confidence: low
+verify:
+  method: GET
+  url: https://api.baseten.co/v1/models
+  headers:
+    Authorization: "Api-Key {KEY}"
+  valid_status: [200]
+  invalid_status: [401, 403]