data: exam dates go stale silently — June 2026 IGCSE results date has already passed

[shauryagangrade]

Problem

src/lib/exam-dates.ts is a static array with a manual "Last verified: 2026-06-11" header. The Cambridge June 2026 series lists results: "2026-08-18" — three days ago as of filing — yet it still renders like any other upcoming entry. Nothing in CI or tests flags when entries age out, so the calendar will keep drifting.

Suggested fix

1. Add a unit test that fails when an event's date/results date is in the past and it isn't explicitly marked as completed/archived (or auto-flag past events in the UI with a "passed" style)
2. Optionally add a scheduled CI job (monthly) that opens/updates an issue listing entries needing re-verification
3. Consider deriving a visible "Last verified" per-series date from git history or a field, instead of one global header

Acceptance criteria

• Past events are visually distinguishable from upcoming ones
• CI catches silently-stale entries