Add Provider Package

When you need to integrate a new AI provider into the Vercel AI SDK as an official @ai-sdk package, this walks you through the entire setup. It covers the layered architecture (specifications, utilities, providers, core), shows you how to structure your package directory, and explains the adapter pattern for implementing LanguageModelV4, EmbeddingModelV4, and other model types. The guide is thorough on the details that matter: using workspace dependencies, configuring both Node and Edge tests, handling API keys with loadApiKey, and the critical distinction between user-facing schemas (use .optional) and API response schemas (use .nullish). It also covers the less obvious stuff like running pnpm update-references after setup and why you shouldn't create a CHANGELOG.md file yourself.