* test/s3vectors: data-plane lifecycle integration test
TestVectorDataPlaneLifecycle spawns a real weed-vector against the lance
listener, mirrors the pytest cluster's flags, waits for the gateway to
discover the registered engine, and walks the full lifecycle: create
bucket and index, put/get/list vectors, a filtered query that excludes the
nearer non-matching vector, delete vectors, index, and bucket. The test
skips when no engine binary resolves (VECTOR_BINARY, ./weed-vector, PATH).
* test/s3vectors: fail fast when the engine dies before listening
* test/s3vectors: harden engine launch and tighten lifecycle assertions
* test/s3vectors: wait on the engine's exit once through a broadcast channel