Summary

• mark background ranked jobs as failed when public execution completes but required secret validation does not qualify the submission
• include a clear job error explaining that the submission will not appear on the leaderboard
• add regression coverage for a public-passed, secret-failed ranked submission

Root Cause

Background submissions treated successful runner completion as job success. Ranked submissions can complete runner execution while failing secret validation, leaving the leaderboard correctly unscored but the job status misleadingly marked succeeded.

Impact

Users polling submission status now see a failed job with an actionable secret-validation message instead of succeeded with no leaderboard score.

Validation

• uv run --extra dev ruff check src/libkernelbot/background_submission_manager.py tests/test_background_submission_manager.py
• uv run --extra dev pytest tests/test_background_submission_manager.py

DB-backed backend/leaderboard tests were attempted locally but Docker was unavailable (/Users/mark/.docker/run/docker.sock missing), so those should run in CI.