Add gRPC support when proto definitions become available

[K-dash]

Description

Currently, this CLI uses the REST API to communicate with NotebookLM. Once Google publishes the official gRPC proto definitions for NotebookLM, we should add gRPC support as an alternative transport method.

Background

• The NotebookLM API is currently in alpha and only provides REST endpoints
• gRPC typically offers better performance and streaming capabilities
• Official proto definitions are not yet available as of 2025-10-19

Tasks

• Monitor for official gRPC proto release
• Add gRPC client implementation alongside existing REST client
• Add CLI flag to choose between REST/gRPC (e.g., --protocol grpc)
• Update documentation with gRPC usage examples
• Add integration tests for gRPC endpoints

References

• NotebookLM API Documentation

Priority

Low - blocked until proto definitions are published by Google