feat(plugin): expose synthetic session input (#37212)

packages/core/src/plugin/host.ts

@@ -425,6 +425,7 @@ export const make = Effect.fn("PluginHost.make")(function* (plugin: PluginV2.Int
       get: (input) => runtime.session.get(input.sessionID),
       prompt: runtime.session.prompt,
       command: runtime.session.command,
+      synthetic: runtime.session.synthetic,
       interrupt: (input) => runtime.session.interrupt(input.sessionID),
     },
   } satisfies Plugin.Context