nx_install_pipeline_test.nx

nx_install_pipeline_test.nx -- smoke for the SA arc end-to-end orchestrator nx_install_pipeline_run_with_inputs. Exercises: 1. BAD_INPUT gates (null probe / calib / policy / nodes / out) 2. Successful 3-node chain produces VALID plan + 32-byte hash that matches direct (capture + hash) recomputation 3. End-to-end REPRODUCIBILITY: same inputs -> bit-equal install_hash 4. End-to-end SENSITIVITY: change probe.page_size -> different hash 5. SELECT_FAILED path: no-feasible-chain produces NX_PIPELINE_SELECT_FAILED with zero'd install_hash + plan carrying NX_PLAN_VERDICT_NO_FEASIBLE 6. Sealed-enum validity gate This is the LOAD-BEARING end-to-end gate for the SA arc: it proves the chain (probe + calibration + policy + workload-DAG) -> single install_hash works as a pure composition, and that the hash is both reproducible and sensitive to content.