[codex] Harden Smart Agent GitHub Actions workflows

[chambear2809]

Summary

• Upgrade workflow checkouts to actions/checkout@v6 for Node 24-compatible action runtime.
• Fail remote lifecycle jobs when Smart Agent emits JSON with "error": true, even if the command exits zero.
• Verify Smart Agent service health after deploy and remove temporary deployment artifacts from target hosts.
• Fix uninstall workflow dependencies so API checks and summaries reference the actual uninstall-batch job.
• Add a small shell test for Smart Agent output error detection.

Validation

• shellcheck .github/scripts/*.sh
• bash .github/scripts/test-lib.sh
• bash .github/scripts/test-create-batches.sh
• bash .github/scripts/test-client-inventory-api.sh
• jq empty openapi.json
• yamllint .github/workflows/*.yml
• go run github.com/rhysd/actionlint/cmd/actionlint@latest .github/workflows/*.yml
• git diff --check

Live Lab Notes

• Runner smartagent-demo is online and idle.
• smartagent.service is active on all configured target hosts.
• Machine Agent install currently reports a Smart Agent extraction error for the bundled otel collector on three targets; with this change that condition will fail the workflow instead of being hidden as success.