test: isolate release lab environment assumptions

[chubes4]

Summary

• isolate agent runtime component discovery from inherited deployment configuration
• recognize terminated Linux zombie descendants as stopped
• sample host command process groups again after the child spawn event
• exercise RSS artifact capture with an executor-bounded persistent command, preserving timeout and output assertions

Validation

• wp-codebox-2484-final-host-command: pass on homeboy-lab after normal npm ci applied the required Playground patch
• wp-codebox-2484-full-8way-1: pass, npm run smoke -- --all --concurrency=8 on homeboy-lab
• wp-codebox-2484-full-8way-2: pass, same Git-backed workspace and command
• GitHub CI is pending for pushed head 962ca314c6abab45fed1655c32b3d843aa3e5938.

AI assistance

Used GPT-5.6-terra via OpenCode to diagnose the lab-only failures, implement scoped host-command sampling and test corrections, and run Git-backed lab validation.