Announce a doorbell with proactivelyReported and a scene with supportsDeactivation

An interface without properties says beside its name what Alexa has to know
of it; the library left both out. With a board and Alexa on 2026-09-28 the
discovery of a doorbell was accepted (202), the endpoint was not listed, and
its DoorbellPress was answered with 500 INTERNAL_SERVICE_EXCEPTION.

DoorbellEventSource now always carries "proactivelyReported": true.
SceneController carries "supportsDeactivation", false until the sketch calls
setSupportsDeactivation(true); on another interface the call is refused and
logged. The Scene example says that it can be undone.

148 host tests. Light: static RAM 30,616 B, flash 332,705 B (+140 B).

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

readme.md

@@ -685,7 +685,6 @@ What changes for a 1.x sketch that is compiled against 2.0:
 - Reports are published with QoS 0 and sent once. An event or a change while there is no session with the broker is not sent later; `send()` returns `false` and the sketch decides.
 - Tried with Alexa from this library: the six interfaces marked in [Interface Types](#interface-types). Not tried from this library: `ColorController`, `ThermostatController`, `LockController` and the deferred answer, `SceneController`, the ErrorResponse, the ChangeReports, `DoorbellPress` and every interface without an example. Voice commands have not been tried.
 - The examples are compiled, with 0 warnings, and what each announces in discovery is checked by the host tests. They have not run on a board and have not been built with the Arduino IDE.
-- The discovery object of a scene does not carry `supportsDeactivation`, so Alexa may never send `Deactivate`.
 - The library keeps no state of the devices. What a device is set to is a variable of the sketch and starts from its initial value after a reset.
 - 28 of the interfaces of Alexa have a row. The others cannot be announced.
 - The Arduino IDE builds with the default limits.