vLLM gRPC API

Protocol definitions for the optional gRPC server exposed by the vLLM Rust frontend.

• Inference provides unary and streaming generation.
• Control provides discovery and request control.

The nightly label is updated daily from vLLM's main branch. The main label tracks the latest vLLM release, and version labels match tags such as v0.27.0. Pin a Buf commit or generated SDK version for reproducible builds.