[rajeeja]

Summary

• clear stale PMI_FD/PMI_RANK/PMI_SIZE before YAC-backed worker remaps
• apply the same environment to the remote YAC smoke probe
• replace the misleading MPI-launcher recommendation with the measured singleton diagnosis
• update Chrysalis/UCAR endpoint scripts and UCAR documentation
• add regression tests covering all three serialized worker remap paths

Validation

• 1567 passed, 1 skipped, 44 deselected, 1 xfailed
• docs build with -W clean
• shell syntax and shellcheck clean
• Chrysalis live conservative remap: 10/10 matrix after the fix
• UCAR live check_remote_yac: conservative_ok: true; full matrix remains 13/14 because the endpoint's remap_to_rectilinear path is still failing independently
• direct Chrysalis in-worker test: conservative YAC remap succeeds with PMI_FD removed, matching the local result

The fix intentionally does not add an MPI launcher. Testing showed that multi-rank invocation without explicit gather logic returns silently incorrect, non-deterministic results.