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/perplexity-web.js

@@ -0,0 +1,39 @@
+export default {
+  "id": "perplexity-web",
+  "alias": "perplexity-web",
+  "transport": {
+    "baseUrl": "https://www.perplexity.ai/rest/sse/perplexity_ask",
+    "format": "perplexity-web",
+    "authType": "cookie"
+  },
+  "models": [
+    {
+      "id": "pplx-auto",
+      "name": "Perplexity Auto (Free)"
+    },
+    {
+      "id": "pplx-sonar",
+      "name": "Perplexity Sonar"
+    },
+    {
+      "id": "pplx-gpt",
+      "name": "GPT-5.4 (via Perplexity)"
+    },
+    {
+      "id": "pplx-gemini",
+      "name": "Gemini 3.1 Pro (via Perplexity)"
+    },
+    {
+      "id": "pplx-sonnet",
+      "name": "Claude Sonnet 4.6 (via Perplexity)"
+    },
+    {
+      "id": "pplx-opus",
+      "name": "Claude Opus 4.6 (via Perplexity)"
+    },
+    {
+      "id": "pplx-nemotron",
+      "name": "Nemotron 3 Super (via Perplexity)"
+    }
+  ]
+};