NotebookLM API Restored with Stricter Schema Constraints

The notebooks resource is back with create, get, batchDelete, and listRecentlyViewed methods. This re-rollout includes significant breaking changes: numerous fields across GoogleCloudNotebooklmV1alphaNotebook, GoogleCloudNotebooklmV1alphaSource, and metadata schemas (Youtube, Google Docs, Agentspace) have been marked as read-only or immutable. Furthermore, name and parent parameters are now strictly required for these methods, necessitating updates to existing client implementations to ensure these fields are provided in requests.