AlexaStatusMessage: DeferredResponse, ChangeReport, ErrorResponse, scene and doorbell events, UUID-shaped messageId

A message has a kind, and the kind decides its topic: answers on
<root>/<id>/alexaResponce, the answer after a DeferredResponse on
<root>/<id>/deferredResponse (sendAsync()), a ChangeReport on
<root>/changeReport with the changed properties apart from the others
(context()), DoorbellPress on <root>/event. AlexaDirective gains deferred(),
error(type, message), sceneStarted() and sceneStopped(); thermostat error
types go out in the namespace of the thermostat. The helpers are add*Prop,
the Add*Prop names stay; a temperature keeps its scale (69 FAHRENHEIT, was
20.56 CELSIUS). messageId is a version 4 UUID from the hardware random
source, where rand() seeded per second gave two messages one id.
basicLight: static RAM 30,540 B (-76), flash 334,981 B (+1,280);
112 host tests (bridge logic 52, messages 19, new).

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

src/AlexaCompat.h

@@ -1,6 +1,6 @@
 // Lets the sources that have no hardware dependency compile on a host (pio test -e native), where the
 // program-memory helpers of the Arduino cores do not exist: there a PROGMEM object is an ordinary constant and a
-// pointer to one an ordinary pointer. On a board this is Arduino.h and nothing else.
+// pointer to one an ordinary pointer. On a board this is Arduino.h and the random source of the hardware.
 #ifndef ALEXA_COMPAT_H
 #define ALEXA_COMPAT_H
 
@@ -9,6 +9,7 @@
 #else
 #include <stdint.h>
 #include <string.h>
+#include <random>
 #define PROGMEM
 #define PGM_P const char *
 #define PSTR(text) (text)
@@ -20,4 +21,17 @@
 #define strncpy_P strncpy
 #endif
 
+// 32 bits that cannot be predicted and differ after every reset
+inline uint32_t alexaRandom32()
+{
+#if defined(ESP8266)
+    return RANDOM_REG32; // fed by the noise of the radio
+#elif defined(ESP32)
+    return esp_random(); // ESP32: untested
+#else
+    static std::random_device source;
+    return source();
+#endif
+}
+
 #endif // ALEXA_COMPAT_H