3288 Update Checker

Added

• RetroArch dylib update checker — check-dylib-updates.sh queries the buildbot for the latest nightly date, reports when a newer snapshot is available, and can auto-bump cores.yml with --update.
• Staleness warning — get-modules.sh now emits a build-time warning when pinned_date is more than 30 days old, prompting developers to run the update checker.