- custom-apps
	- not shipped with the system; installed on top
	- same mechanics as core-apps (manifest, router, migrations, events, DI) — loader does not distinguish
	- typically declared required: false → can be switched off; can declare conflicts_with to prevent incompatible pairs
	- two categories: optional apps (same team, shipped later) and third-party apps (marketplace, external developers)
	- planned optional apps (from base.md): wishlist, reviews, coupons / discount engine, product recommendations, multi-vendor, subscriptions
	- room for growth: app signing / verification, loader version-compat checks, per-app permission declarations, isolated migration namespaces, install/uninstall lifecycle hooks, marketplace registry