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/models/helpers.js

@@ -0,0 +1,20 @@
+// Codex auto-generates a "-review" variant for each llm model (review quota family)
+const CODEX_REVIEW_SUFFIX = "-review";
+
+export function withCodexReviewModels(models) {
+  return models.flatMap((model) => {
+    if ((model.type || "llm") !== "llm" || model.id.endsWith(CODEX_REVIEW_SUFFIX)) {
+      return [model];
+    }
+    return [
+      model,
+      {
+        ...model,
+        id: `${model.id}${CODEX_REVIEW_SUFFIX}`,
+        name: `${model.name} Review`,
+        upstreamModelId: model.upstreamModelId || model.id,
+        quotaFamily: "review"
+      }
+    ];
+  });
+}