messages: DoorbellPress is sent with the empty context of its page

proactiveEvent() built every proactive event without a context, so doorbellPress() and
device.raise(DoorbellEventSource, "DoorbellPress") left out the "context": {} that the example of
alexa-doorbelleventsource.html has. The Event of Alexa.SimpleEventSource is printed without one, so
the event descriptor says which it is (emptyContext) and raise() passes it on to the builder.

A raised DoorbellPress is now { event, context: {} }, 13 bytes longer; the Event of a button is
unchanged. The tests compare the keys and the context of the built message with the fixture of the
page, for the builder, the descriptor and raise(). 267 tests pass.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

dist/cjs/device/Device.js

@@ -181,6 +181,7 @@ class Device extends events_1.EventEmitter {
             instance,
             payloadVersion: event.payloadVersion ?? capability.descriptor.version,
             payload: checked,
+            emptyContext: event.emptyContext,
         });
         const bytes = Buffer.byteLength(JSON.stringify(message));
         if (bytes > topics.EVENT_BYTES)