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/

pkg/providers/definitions/together.yaml

@@ -0,0 +1,22 @@
+format_version: 1
+name: together
+display_name: Together AI
+tier: 2
+last_verified: "2026-04-05"
+keywords:
+  - "together"
+  - "togetherai"
+  - "TOGETHER_API_KEY"
+  - "api.together.xyz"
+  - "api.together.ai"
+patterns:
+  - regex: '[a-f0-9]{64}'
+    entropy_min: 3.5
+    confidence: low
+verify:
+  method: GET
+  url: https://api.together.xyz/v1/models
+  headers:
+    Authorization: "Bearer {KEY}"
+  valid_status: [200]
+  invalid_status: [401, 403]