[jmgirard]

Adds a second independent check to three results that each rested on one kind of check, or none. No package code changes.

• compute_metrics() on a censored run: static, dynamic and linear-predictor survival metrics are now checked against collect_metrics(), against yardstick called on each fold's rows, and by reversing one prediction column at a time. The tests run six mixes of metric kinds, so each branch of the scorer is reached.
• The racing record's rows for eliminated candidates are checked against the grid path over an inner design cut to the resamples the race scored them on.
• The final fit's tuning run under event_level = "second" is checked by counting sensitivity and specificity from its saved predictions.

cairn/ORACLES.md records the new checks.

Candidate row: Add second oracles to one-type parts