Scheduled CI check that flags stale catalog snapshots

[TianCZeng]

Problem

Records in programs/catalog/ are dated snapshots of official pages — each
carries retrieved_at and its source URLs. Official pages change, so a
catalog that was accurate when retrieved can silently ship stale deadlines
months later. The README frames every record as a dated snapshot, but nothing
actively tells the maintainer "this snapshot is now old."

Proposal

A scheduled GitHub Actions workflow (weekly cron) that:

• scans every record in programs/catalog/;
• flags records whose retrieved_at is older than a threshold (proposal:
  90 days, configurable in the workflow);
• fails the scheduled run — or opens/updates a single tracking issue —
  listing each stale record with its official URL, so it can be re-verified
  against the live page.

It must not run on pull requests: contributors should never be blocked by
calendar drift they didn't cause. Freshness is a maintenance signal, not a
merge gate.

Acceptance criteria

• New workflow under .github/workflows/ with schedule: and
  workflow_dispatch: triggers only.
• Output lists each stale record's id, retrieved_at, and official URL.
• Reuses the existing catalog parsing from scripts/verify/catalog.js where
  practical rather than re-implementing YAML handling.