Drives `vllm-omni serve <model> --omni` as a subprocess through the
online-serving launcher and checks /health, /v1/models, non-streaming
and streaming chat completions, and that a client disconnect mid-stream
leaves the server answering. Sets VLLM_USE_FLASHINFER_SAMPLER=0 like
LocalTextEngine does: the flashinfer sampler JITs with nvcc at runtime,
which a venv without a CUDA toolkit does not have (measured: the WSL
reference venv died in profile_run with 'Could not find nvcc').
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
