feat(ai): derive generated model types from JSON

packages/ai/README.md

@@ -1533,7 +1533,7 @@ Compat is a strict superset of the root entrypoint, so a file can switch its imp
 
 ### Adding a New Provider
 
-Adding a new LLM provider requires changes across multiple files. The layered layout: API implementations live in `src/api/`, provider factories in `src/providers/`, generated catalogs in `src/providers/<id>.models.ts`. This checklist covers all necessary steps:
+Adding a new LLM provider requires changes across multiple files. The layered layout: API implementations live in `src/api/`, provider factories in `src/providers/`, stable generated catalog wrappers live in `src/providers/<id>.models.ts`, and `src/models.generated.ts` registers them. This checklist covers all necessary steps:
 
 #### 1. Core Types (`src/types.ts`)
 
@@ -1555,7 +1555,7 @@ Add a lazy wrapper `src/api/<api-id>.lazy.ts` (`<name>Api()` via `lazyApi()`) so
 #### 3. Model Generation (`scripts/generate-models.ts`, `scripts/generate-image-models.ts`)
 
 - Add logic to fetch and parse models from the provider's source (e.g., models.dev API)
-- Map chat/tool-capable provider model data to the standardized `Model` interface via `scripts/generate-models.ts`; regeneration emits structural `src/providers/<id>.models.ts` shards, ignored values in `src/providers/data/`, and the aggregator
+- Map chat/tool-capable provider model data to the standardized `Model` interface via `scripts/generate-models.ts`; hydration groups the ignored `src/providers/data/<id>.json` values by API, while stable `src/providers/<id>.models.ts` wrappers derive exact model/API types directly from those JSON keys
 - Map image-generation provider model data to the standardized `ImagesModel` interface via `scripts/generate-image-models.ts`
 - Handle provider-specific quirks (pricing format, capability flags, model ID transformations)