Instrument Copilot execution step to persist stderr and exit code on failure

[Copilot]

Deep-report analysis found the dominant Copilot failure mode was 0-turn/0-token exits from Execute GitHub Copilot CLI with no stderr captured in artifacts, making failures non-diagnosable. This change instruments the generated Copilot execution step to always emit failure diagnostics into the existing log artifact path.

• Failure diagnostics in generated Copilot run step

  • Wraps the existing Copilot command in a failure-aware shell envelope.
  • Captures stderr to /tmp/gh-aw/sandbox/agent/logs/copilot-cli-exec.stderr.log while preserving stderr in live job logs.
  • Captures non-zero exit status to /tmp/gh-aw/sandbox/agent/logs/copilot-cli-exec.exitcode.
  • Re-exits with the original Copilot exit code to preserve current failure semantics.
  • Cleans stale diagnostic files at start; removes stderr artifact on success to keep artifacts failure-focused.

• Execution-step contract updates

  • Updates Copilot execution-step tests to assert presence of stderr/exit-code capture behavior.
  • Refreshes impacted Copilot workflow golden outputs to reflect generated YAML changes.

mkdir -p /tmp/gh-aw/sandbox/agent/logs/
rm -f /tmp/gh-aw/sandbox/agent/logs/copilot-cli-exec.stderr.log /tmp/gh-aw/sandbox/agent/logs/copilot-cli-exec.exitcode
set +e
(
  # existing Copilot command
) 2> >(tee -a /tmp/gh-aw/sandbox/agent/logs/copilot-cli-exec.stderr.log >&2)
GH_AW_COPILOT_EXEC_EXIT_CODE=$?
set -e
if [ "$GH_AW_COPILOT_EXEC_EXIT_CODE" -ne 0 ]; then
  printf '%s\n' "$GH_AW_COPILOT_EXEC_EXIT_CODE" > /tmp/gh-aw/sandbox/agent/logs/copilot-cli-exec.exitcode
fi
exit "$GH_AW_COPILOT_EXEC_EXIT_CODE"

[github-actions]

🤖 PR Triage — Run §28572743533

Field	Value
Category	feature
Risk	🟡 Medium
Score	64 / 100
Breakdown	Impact: 30 · Urgency: 20 · Quality: 14
Action	fast_track

Adds stderr/exit-code persistence on Copilot execution failure — high-value debugging capability across 7 files. Recommend expedited human review once undrafted.

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