docs: add communication environment baseline

[Kur0x]

Summary

• require matching official HCCL Test coverage before debugging communication or device-dependent failures
• judge the environment baseline from per-rank correctness output, not exit status alone
• stop operator-side debugging when the matching HCCL Test shows the environment is unhealthy

Validation

• verified the new section and required commands appear exactly once
• git diff --check

Documentation-only change; no build or hardware tests were run.