Fix review follow-up queue and settings state

[cbusillo]

Summary

• count all distinct recent calibration terminal prefixes, while keeping the displayed rows lane-limited
• clear stale settings save/archive feedback when the settings payload disappears after a load failure
• strengthen queue summary regression coverage beyond the old prefetch window

Validation

• uv run --with pytest pytest tests/test_encode_queue_recovery.py -k 'calibration_queue_summary_counts_recent_failures_beyond_display_limit or calibration_queue_summary_limits_recent_failed_jobs_per_lane or calibration_queue_summary_deduplicates_failed_prefixes_before_limit'
• npm --prefix frontend run check
• bash scripts/pre-commit-check.sh