feat(03-01): add 8 Tier 4 Chinese providers (DeepSeek, Zhipu, Moonshot, Qwen, Baidu, ByteDance, 01.AI, MiniMax)

- DeepSeek, Moonshot, Qwen use documented sk- prefix patterns
- Zhipu, Baidu, ByteDance use keyword-only detection (no documented key format)
- All dual-located in providers/ and pkg/providers/definitions/

providers/minimax.yaml

@@ -0,0 +1,18 @@
+format_version: 1
+name: minimax
+display_name: MiniMax
+tier: 4
+last_verified: "2026-04-05"
+keywords:
+  - "minimax"
+  - "MINIMAX_API_KEY"
+  - "MINIMAX_GROUP_ID"
+  - "api.minimax.chat"
+  - "abab6"
+verify:
+  method: GET
+  url: https://api.minimax.chat/v1/text/chatcompletion_v2
+  headers:
+    Authorization: "Bearer {KEY}"
+  valid_status: [200, 400]
+  invalid_status: [401, 403]