STCP GitHub Actions artifact/failure-order fix

Files:

• .github/workflows/build.yml
• .github/workflows/benchmark.yml
• .github/workflows/stcp-overnight-benchmark.yml

Main changes:

1. Long build/benchmark steps use continue-on-error: true and expose their outcome.
2. Result discovery, summaries and artifact uploads run before the job is failed.
3. Artifact uploads use if: always() && !cancelled() and continue-on-error: true.
4. A final explicit failure step restores the correct failed job status after uploads.
5. Artifact names include github.run_id and github.run_attempt, preventing name collisions on reruns.
6. Golden tags are created only when the overnight benchmark step really succeeded.

Install from repository root:

unzip stcp-workflows-artifact-fix.zip -d /tmp/stcp-workflow-fix
cp /tmp/stcp-workflow-fix/.github/workflows/*.yml .github/workflows/