Surface unranked leaderboard submissions

[msaroufim]

Summary

• make completed leaderboard submissions without a qualifying public score plus secret validation fail in the submit polling flow
• show not ranked in submission lists when a completed submission has no ranked runs
• show server job status and job error in submission details
• add unit coverage for secret failures, missing secret leaderboard validation, missing public scores, and non-leaderboard modes

Root Cause

The CLI exited successfully once the server marked a submission done unless the job status was explicitly failed. That made legacy or in-flight succeeded jobs with no qualifying leaderboard score look like successful submissions.

Impact

Leaderboard submissions that pass public validation but fail secret validation now surface a clear CLI error instead of printing successful JSON with an empty or unscored result.

Validation

• cargo fmt --all -- --check
• cargo test
• cargo clippy --all-targets --all-features -- -D warnings