refactor(schema): extract public event definitions (#33579)

packages/schema/src/plugin.ts

@@ -0,0 +1,15 @@
+export * as Plugin from "./plugin"
+
+import { Schema } from "effect"
+import { define, inventory } from "./event"
+
+export const ID = Schema.String.pipe(Schema.brand("Plugin.ID"))
+export type ID = typeof ID.Type
+export const PluginID = ID
+
+const Added = define({
+  type: "plugin.added",
+  schema: { id: ID },
+})
+export const Event = { Added, Definitions: inventory(Added) }
+export const PluginEvent = Event