#814 Activity remote context missing 'now' -> non-waiting app with ctx.now fails when routed to activity worker (#agentic)

A non-waiting app with a timeout_policy > 30s routes to the activity worker; if the app calls ctx.now it fails: 'Remote Error (AttributeError): Method now not found on DurableContext'. #738 added the now @property to the IPC ProxyDurableContext, but the ACTIVITY worker's remote context path lacks the same fix. Repro: apps.platform.hello_world.greet as a task with timeout_policy=60s -> activity -> fails. Fix: add the now property/coercion to the activity remote-context proxy too (mirror #738).