feat(03-01): add 8 Tier 4 providers (Baichuan, StepFun, SenseTime, iFlytek, Tencent, SiliconFlow, 360AI, Kuaishou)

- SiliconFlow uses documented sk- prefix
- Other 7 keyword-only (no documented key format, avoids false positives)
- Completes PROV-04: 16 Tier 4 Chinese/regional providers

providers/siliconflow.yaml

@@ -0,0 +1,21 @@
+format_version: 1
+name: siliconflow
+display_name: SiliconFlow
+tier: 4
+last_verified: "2026-04-05"
+keywords:
+  - "siliconflow"
+  - "SILICONFLOW_API_KEY"
+  - "api.siliconflow.cn"
+  - "siliconflow.cn"
+patterns:
+  - regex: 'sk-[a-z]{20,}'
+    entropy_min: 3.5
+    confidence: low
+verify:
+  method: GET
+  url: https://api.siliconflow.cn/v1/models
+  headers:
+    Authorization: "Bearer {KEY}"
+  valid_status: [200]
+  invalid_status: [401, 403]