refactor(open-sse): P3 provider registry — split into providers/registry/{id}.js

- 100 registry files: transport + models co-located per provider (Mongoose-style)
- providers/shared.js: shared Claude headers + OS/arch helpers (deduped)
- providers/models/helpers.js: withCodexReviewModels (kept dynamic)
- providers/index.js builds PROVIDERS + PROVIDER_MODELS = old API (content byte-for-byte)
- config/providers.js + providerModels.js → barrel re-export, keep accessors + runtime helpers
- Verified: PROVIDERS/MODELS/OAuth/alias byte-for-byte, golden translator tests pass, 0 new regression

Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/providers/registry/deepseek.js

@@ -0,0 +1,35 @@
+export default {
+  "id": "deepseek",
+  "alias": "deepseek",
+  "transport": {
+    "baseUrl": "https://api.deepseek.com/chat/completions"
+  },
+  "models": [
+    {
+      "id": "deepseek-v4-pro",
+      "name": "DeepSeek V4 Pro"
+    },
+    {
+      "id": "deepseek-v4-pro-max",
+      "name": "DeepSeek V4 Pro Max",
+      "upstreamModelId": "deepseek-v4-pro"
+    },
+    {
+      "id": "deepseek-v4-pro-none",
+      "name": "DeepSeek V4 Pro No Thinking",
+      "upstreamModelId": "deepseek-v4-pro"
+    },
+    {
+      "id": "deepseek-v4-flash",
+      "name": "DeepSeek V4 Flash"
+    },
+    {
+      "id": "deepseek-chat",
+      "name": "DeepSeek V3.2 Chat"
+    },
+    {
+      "id": "deepseek-reasoner",
+      "name": "DeepSeek V3.2 Reasoner"
+    }
+  ]
+};