feat(kiosk): plugin.yaml manifest and summer plugin:manifest

- new module kiosk: Manifest, Marshal, Parse, Derive, Generate, Write, Check, StaleError
- plugin:manifest [dir] with --check, --pretend, --name, --description
- docs: kiosk README, root table row, plugins/marketplace.md, scaffolding row

README.md

@@ -105,6 +105,7 @@ The `migrate`, `migrate:status`, `migrate:rollback`, `serve` and admin commands
 | [festival](modules/festival/README.md) | Typed, synchronous event bus with listener priorities, payload collection and stop-when-handled dispatch. | A summer festival announces events and the crowd reacts; it is the event bus. |
 | [fetchguard](modules/fetchguard/README.md) | Guarded outbound HTTP client and fetcher that blocks private and reserved addresses, enforces host, size and timeout limits, and offers an explicit trusted mode for operator-configured endpoints. | A lifeguard for outbound fetches; it watches every request the application sends out and stops the dangerous ones. |
 | [flare](modules/flare/README.md) | Web Push delivery with VAPID (RFC 8292) and aes128gcm payload encryption (RFC 8291) behind a small Pusher interface. | A signal flare reaches people far away; it sends Web Push notifications to browsers. |
+| [kiosk](modules/kiosk/README.md) | Plugin manifests and the plugin registry contract: generates and checks each plugin's plugin.yaml from its own sources. | A beach kiosk where every plugin on the shelf carries its label; the label is printed from what is in the box, never written by hand. |
 | [lagoon](modules/lagoon/README.md) | Postgres data layer: the shared GORM connection, per-plugin migrations, model helpers and file attachments. | Calm, deep water where everything settles; it is the database layer where data is stored. |
 | [lighthouse](modules/lighthouse/README.md) | Transport-neutral realtime: a publisher interface with pluggable drivers, subscribe-time channel authorization, and model broadcasts enqueued in the write transaction. | Beams a signal out to everyone watching; it broadcasts realtime messages to subscribers. |
 | [pact](modules/pact/README.md) | Capability interfaces that compiled plugins implement to contribute routes, config, migrations, middleware, commands, admin screens, translations, mail templates and jobs. | An agreement both sides keep; it holds the interfaces a plugin agrees to implement. |