messages: pure builders for every event the bridge sends

src/messages builds Response, StateReport, DeferredResponse, ErrorResponse, ChangeReport and the scene, doorbell
and simple events from plain values; messageId and times are parameters, so a test compares whole objects.
StateBuilder collects properties checked by the descriptors, AlexaError and AlexaErrors carry the payload fields
of an error type. AlexaStatusMessage and AlexaErrorResponse move to src/compat and are written on the builders.
On the wire, against 1.5.2: a DeferredResponse has no context key, a ChangeReport has no correlationToken, the
namespace of an ErrorResponse follows its type, and a ChangeReport without a changed property is not published:
send() resolves "" and the bridge reports an error that names the endpoint.
143 tests pass (108 before).

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

dist/esm/messages/build.d.ts

@@ -0,0 +1,97 @@
+import type { ChangeCause, ChangeReportMessage, DeferredResponseMessage, ErrorResponseMessage, ProactiveEventMessage, Property, ResponseMessage, SceneEventMessage } from "./types.js";
+/** A message that would be dropped on its way to Alexa, refused where it is built. */
+export declare class MessageError extends Error {
+    readonly endpointId: string;
+    readonly problem: string;
+    constructor(endpointId: string, problem: string);
+}
+interface Envelope {
+    endpointId: string;
+    /** Default: a new version 4 UUID, which is what Alexa recommends (message-guide.html, "Header object"). */
+    messageId?: string;
+}
+interface Answer extends Envelope {
+    /** The correlationToken of the directive that is answered. */
+    correlationToken: string;
+}
+export interface ResponseFields extends Answer {
+    /** Default: "Response". */
+    name?: string;
+    /** Default: "Alexa". An interface with a response of its own names it: Alexa.SecurityPanelController, Arm.Response. */
+    namespace?: string;
+    payload?: Record<string, unknown>;
+    /** The state of the endpoint after the directive. */
+    context?: readonly Property[];
+}
+/**
+ * The answer to a directive (alexa-response.html, "Synchronous response"). An endpoint with nothing to report
+ * answers with an empty list of properties, not without a context (state-reporting-for-smart-home-addons.html,
+ * "Directive response example for a property that isn't retrievable").
+ */
+export declare function response(fields: ResponseFields): ResponseMessage;
+/** The answer to ReportState: every retrievable property of the endpoint. */
+export declare function stateReport(fields: Answer & {
+    context?: readonly Property[];
+}): ResponseMessage;
+/**
+ * "The directive arrived, the answer follows": no context, the state is in the Response that follows
+ * (alexa-response.html, "Deferred response example").
+ */
+export declare function deferredResponse(fields: Answer & {
+    estimatedDeferralInSeconds?: number;
+}): DeferredResponseMessage;
+export interface ErrorResponseFields extends Answer {
+    /** "ENDPOINT_UNREACHABLE" */
+    type: string;
+    /** For the log of the skill. */
+    message: string;
+    /** The fields a type adds to the payload: validRange, currentDeviceMode. */
+    extra?: Record<string, unknown>;
+    /** Default: the namespace the type is documented under, see errorNamespace(). */
+    namespace?: string;
+}
+/** The answer to a directive the endpoint could not follow (alexa-errorresponse.html). */
+export declare function errorResponse(fields: ErrorResponseFields): ErrorResponseMessage;
+export interface ChangeReportFields extends Envelope {
+    /** Default: "PHYSICAL_INTERACTION". */
+    cause?: ChangeCause;
+    /** The properties that changed, at least one. */
+    changed: readonly Property[];
+    /** The other properties of the endpoint, as they are now. */
+    context?: readonly Property[];
+}
+/**
+ * A change of state nobody asked for. The header has no correlationToken (message-guide.html, "Header object").
+ * A property that changed is left out of the context: it is reported in one of the two (same page, "Context
+ * object"). Throws MessageError when nothing changed: Alex2MQTT drops such a report without a word.
+ */
+export declare function changeReport(fields: ChangeReportFields): ChangeReportMessage;
+export interface SceneEventFields extends Answer {
+    /** true: ActivationStarted. false: DeactivationStarted. */
+    activated: boolean;
+    /** Default: "VOICE_INTERACTION", a scene is started by a directive. */
+    cause?: ChangeCause;
+    /** When the scene started. Default: now. */
+    timestamp?: string | Date;
+}
+/** The answer to Activate and Deactivate of a scene (alexa-scenecontroller.html). */
+export declare function sceneEvent(fields: SceneEventFields): SceneEventMessage;
+export interface DoorbellPressFields extends Envelope {
+    /** Default: "PHYSICAL_INTERACTION", somebody pressed the button. */
+    cause?: ChangeCause;
+    /** When the button was pressed. Default: now. */
+    timestamp?: string | Date;
+}
+/** Somebody rang (alexa-doorbelleventsource.html). */
+export declare function doorbellPress(fields: DoorbellPressFields): ProactiveEventMessage;
+export interface SimpleEventFields extends Envelope {
+    /** The instance of Alexa.SimpleEventSource that raises the event. */
+    instance: string;
+    /** The id of the event as discovery listed it: "Button.SinglePush.1". */
+    id: string;
+    /** When the event happened. Default: now. */
+    timestamp?: string | Date;
+}
+/** An event of a button or a sensor that routines start on (alexa-simpleeventsource.html). */
+export declare function simpleEvent(fields: SimpleEventFields): ProactiveEventMessage;
+export {};