Adds a one-shot diagnostic that exercises the lower half of the TP
stack — WorkerPool::spawn, init_nccl, nccl_sanity_check — in isolation
from model load and inference. Runs N-1 worker subprocesses (rank 0
stays in this process), joins them in an NCCL communicator on the
specified CUDA devices, all_reduces a sentinel 1u32 per rank, verifies
the observed_sum equals world_size on every rank, then shuts down.
Output is `status=ok` on stdout (plus key=value lines for tp_size and
cuda_devices) when every check passes, non-zero exit + tracing on
stderr otherwise. The smoke command is diagnostic-only and not exposed
through the daemon HTTP API.
script/tp-smoke.sh wraps it with an ssh invocation against a fleet
host (default beast — the only host with 2 GPUs) and asserts the
status line, mirroring the validate-neuron.sh ergonomics.
This is step 1 of the TP test plan. A failure here means TP cannot
work on the host at all; step 2 (Stage 7b-iv) wires real model load
and inference through the same WorkerPool primitives.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
