[All Platforms][Nemoclaw] nemoclaw debug --output <invalid-path>` reports "Tarball written to ..." even when tar fails; exit code remains 0

[zNeill]

Description

[Environment]
Device: Linux 5.15.0-171-generic x86_64, No GPU
NemoClaw: v0.0.11
OpenShell: N/A
OpenClaw: N/A

[Steps to Reproduce]

1. nemoclaw debug --quick --output /nonexistent/path/debug.tar.gz

[Expected Result]
Command should detect tar failure, report an error, and exit with non-zero status.

[Actual Result]
tar (child): /nonexistent/path/debug.tar.gz: Cannot open: No such file or directory
tar (child): Error is not recoverable: exiting now
tar: Child returned status 2
tar: Error is not recoverable: exiting now
[debug] Tarball written to /nonexistent/path/debug.tar.gz
[debug] Known secrets are auto-redacted...
EXIT_CODE=0

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[NVB# 6065905]