test: avoid broken pipes in monitor runtime checks

[Inference1]

Summary

• replace echo "$output" | grep -q ... assertions in test-monitor-runtime.sh with here-string input
• prevent grep -q from closing the pipe early and causing intermittent echo: write error: Broken pipe failures under set -o pipefail

Testing

• bash tests/test-monitor-runtime.sh — 18 passed, 0 failed (5 consecutive runs)
• bash -n tests/test-monitor-runtime.sh
• git diff --check upstream/dev...HEAD

[Inference1]

@tony-nowatzki Would you please review this pr?

[Inference1]

@tony-nowatzki The CI fixes are pushed and the branch is now synced with dev. GitHub marked the new workflow runs as action_required for this fork PR. Could you please approve the workflow runs? The local monitor runtime suite passes 18/18.