fix(process-registry): avoid background rewrite on env-based spawn

[charzhou]

Summary

• Avoid reapplying compound background rewrites in background wrappers.
• Pass to env.execute so wrapper command is not rewritten into invalid syntax.
• Treat missing PID/failed launch as failed spawn so we never report a fake running session.
• Add registry-level regression tests for launch failure and rewrite bypass.

Testing

• ........................................................................ [ 72%]
  ............................ [100%]
  100 passed in 2.24s

Result

[charzhou]

Closed and recreated with clean history; old PR included unrelated previous commits due branch basis.

[alt-glitch]

Duplicate of #33756 (same author's revised version of this fix). This PR was closed and superseded by #33756.