Dependencies of note

The dependency graph is intentionally split so offline trace tooling stays light while protocol-facing binaries remain pinned to the vLLM line they speak.

• vllm-engine-core-client is a pinned git dependency on vllm-project/vllm (rev in Cargo.toml). The supported-line matrix rewrites this rev from compat.toml; do not let routine dependency tooling bump it.
• nixl-sys is a pinned git dependency on ai-dynamo/nixl, matching the source used when the image builds libnixl. The default build does not compile it; enable nixl for real transfers or nixl-stub for typechecking without libnixl.
• sim-trace is deliberately vLLM-protocol-free. It owns the trace schema, calibration models, Perfetto conversion, and guidellm conversion so analysis tools can build without compiling the protocol stack.