discovery: generate capability JSON from the registry

A capability is a descriptor plus what the endpoint declares (device/Capability.ts), and its discovery object is
generated from the two. The new API is bridge.addDevice({ endpointId, name, categories, ... }) and
device.add(PowerController, options): both throw a DeclarationError that names the endpoint, the interface and
the instance (device/validate.ts), and leave the bridge and the device as they were. AlexaInterface is the same
Capability with the 1.x methods on it; it, ActionMapping and the enums moved to src/compat/, Device to src/device/.

What a 1.x caller can observe:
- every endpoint ends with { type: "AlexaInterface", interface: "Alexa", version: "3" } (alexa-interface.html);
  new Alex2MQTT(..., { alexaInterface: false }) leaves it out
- the fields of a capability object come in the order of Amazon's examples; their content is unchanged
- addCapability() with a name that is not an interface throws (1.5.2 announced it with the version "UNKNOWN")
- ActionMapping takes the payload as an object; a JSON string is parsed (1.5.2 sent the string), any other throws
- what Alexa would reject in a 1.x declaration is not refused: device.check() lists it and the bridge logs each
  line once, as "warning: ..." through the log hook, when it answers a discovery
- a device whose JSON cannot be built is left out of the answer and reported as an error event
- PowerController and EndpointHealth are the descriptors and keep ON/OFF and OK/UNREACHABLE; PowerState is new

Tests: six zoo devices declared the 1.x way give the JSON that Alexa accepted from 1.5.2 on 2026-09-28, plus the
Alexa capability. npm test: 85 pass (was 57) in 10-12 s, also on Node 18.20.8 and 20.20.2.

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

dist/esm/device/Capability.d.ts

@@ -0,0 +1,79 @@
+import type { Declared, Directives, InterfaceDescriptor, Label, Properties, Semantics } from "../registry/types.js";
+/** What a declaration can set for any interface. */
+export interface CommonOptions {
+    /** The name of the instance of a generic controller: "Blind.Lift", "Fan.Speed". */
+    instance?: string;
+    /** What the user calls the instance; the first name is the one the Alexa app shows. */
+    friendlyNames?: Label[];
+    /** The properties are in the answer to ReportState. Default: true. */
+    retrievable?: boolean;
+    /** A change of the properties is sent to Alexa as a ChangeReport. Default: false. */
+    proactivelyReported?: boolean;
+    /** The user can ask for the properties and cannot set them. Left out of discovery when not given. */
+    nonControllable?: boolean;
+}
+/** The same as a schema. The friendly names are checked with the instance, by the rules of the interface. */
+export declare const commonOptions: import("../registry/schema.js").Schema<import("../registry/schema.js").InferShape<{
+    instance: import("../registry/schema.js").OptionalSchema<string>;
+    friendlyNames: import("../registry/schema.js").OptionalSchema<unknown[]>;
+    retrievable: import("../registry/schema.js").OptionalSchema<boolean>;
+    proactivelyReported: import("../registry/schema.js").OptionalSchema<boolean>;
+    nonControllable: import("../registry/schema.js").OptionalSchema<boolean>;
+}>>;
+type Naming<I extends boolean> = I extends true ? {
+    instance: string;
+    friendlyNames: Label[];
+} : {
+    instance?: string;
+    friendlyNames?: Label[];
+};
+/** The options of device.add() for one interface: its own, and the ones every interface has. */
+export type Declaration<O, I extends boolean> = O & Omit<CommonOptions, "instance" | "friendlyNames"> & Naming<I>;
+/** A capability object of a discovery answer (alexa-discovery-objects.html, "Capability object"). */
+export interface CapabilityJson {
+    type: "AlexaInterface";
+    interface: string;
+    instance?: string;
+    version: string;
+    properties?: {
+        supported: Array<{
+            name: string;
+        }>;
+        proactivelyReported: boolean;
+        retrievable: boolean;
+        nonControllable?: boolean;
+    };
+    capabilityResources?: {
+        friendlyNames: Label[];
+    };
+    configuration?: Record<string, unknown>;
+    configurations?: Record<string, unknown>;
+    semantics?: Semantics;
+    [field: string]: unknown;
+}
+/** One interface as an endpoint declares it: the descriptor, and what the declaration says about this endpoint. */
+export declare class Capability<P extends Properties = Properties, D extends Directives = Directives, O = {}> implements Declared<O> {
+    readonly descriptor: InterfaceDescriptor<P, D, O, boolean>;
+    /** The endpoint the capability is declared on; the device sets it. */
+    endpointId: string;
+    /** "" for an interface without instances. */
+    instance: string;
+    friendlyNames: Label[];
+    retrievable: boolean;
+    proactivelyReported: boolean;
+    nonControllable?: boolean;
+    /** The options of the interface: a range, the supported modes, the semantics. */
+    options: O;
+    /** What the bridge logs about the declaration, once, when it answers a discovery. */
+    readonly notes: string[];
+    constructor(descriptor: InterfaceDescriptor<P, D, O, boolean>, declared: CommonOptions & {
+        options: O;
+    });
+    get namespace(): string;
+    /** Mappings of "open", "close", "raise", "lower" and of states, when the declaration has any. */
+    get semantics(): Semantics | undefined;
+    /** The capability object for discovery, its fields in the order of the example on alexa-discovery-objects.html. */
+    toJSON(): CapabilityJson;
+}
+export type AnyCapability = Capability<any, any, any>;
+export {};