registry: describe an Alexa interface as data

src/registry/ holds what the library knows about an interface: namespace, version, the page it was read from,
properties with their value schemas and directives with their payload schemas. Five interfaces are described
(Alexa, PowerController, BrightnessController, TemperatureSensor, EndpointHealth); the other 65 names of
AlexaInterfaceType are stubs with the version and property names of 1.5.2. schema.ts is the run-time check behind
it (241 lines, no new dependency), catalog.ts the vocabularies of the pages: 103 assets (23 units), 6 actions,
9 states, 56 display categories, 22 reserved words, 73 error types under 11 namespaces.

AlexaInterface.getVersion() and getProps() read the registry; the two switch statements are gone (-167 lines).
On the wire: Alexa.EndpointHealth is announced at 3.1 (was 3.3; the page is titled 3.1 and no page mentions 3.3),
and TimeHoldController and Camera.LiveViewController at 3 and 1.7 (1.5.2 sent the string "UNKNOWN").
DisplayCategory gains VACUUM. New exports: registry, DeclarationError, SchemaError, Assets, Units, Actions,
States, DisplayCategories and the descriptor types.

Tests: 20 JSON examples of the five pages under test/fixtures/alexa-docs; every directive payload and property
value in them parses with its descriptor. npm test: 57 pass (was 30) in 10.8 s, also on Node 18.20.8 and 20.20.2.

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

src/registry/index.ts

@@ -0,0 +1,53 @@
+// The interfaces the library knows, by namespace.
+import { Alexa } from "./interfaces/Alexa.js";
+import { BrightnessController } from "./interfaces/BrightnessController.js";
+import { EndpointHealth } from "./interfaces/EndpointHealth.js";
+import { PowerController } from "./interfaces/PowerController.js";
+import { TemperatureSensor } from "./interfaces/TemperatureSensor.js";
+import { STUBS } from "./interfaces/stubs.js";
+import { DeclarationError } from "./types.js";
+import type { AnyDescriptor } from "./types.js";
+
+const described: readonly AnyDescriptor[] = [
+  Alexa,
+  BrightnessController,
+  EndpointHealth,
+  PowerController,
+  TemperatureSensor,
+];
+
+const descriptors = new Map<string, AnyDescriptor>();
+for (const descriptor of [...described, ...STUBS]) {
+  // A stub left in the table next to the descriptor that replaces it would win or lose by the order of this list
+  if (descriptors.has(descriptor.namespace)) throw new Error(`${descriptor.namespace} is described twice`);
+  descriptors.set(descriptor.namespace, descriptor);
+}
+
+export const registry = {
+  /** Whether an interface of this name is known. */
+  has(namespace: string): boolean {
+    return descriptors.has(namespace);
+  },
+
+  /** The descriptor of "Alexa.RangeController" or of AlexaInterfaceType.RANGE_CONTROLLER, which is that string. */
+  get(namespace: string): AnyDescriptor {
+    const descriptor = descriptors.get(namespace);
+    if (!descriptor) throw new DeclarationError({}, `${JSON.stringify(namespace)} is not an interface alex2node knows`);
+    return descriptor;
+  },
+
+  /** Every descriptor, ordered by namespace. */
+  list(): AnyDescriptor[] {
+    return [...descriptors.values()].sort((a, b) => (a.namespace < b.namespace ? -1 : 1));
+  },
+};
+
+export { Alexa, BrightnessController, EndpointHealth, PowerController, TemperatureSensor };
+export { DeclarationError, defineInterface } from "./types.js";
+export type {
+  AnyDescriptor, CapabilityExtras, Declared, DirectiveDescriptor, EndpointView, EventDescriptor, InterfaceDescriptor,
+  Label, PropertyDescriptor,
+} from "./types.js";
+export { s, SchemaError } from "./schema.js";
+export type { Infer, Schema, Temperature, TimeInterval } from "./schema.js";
+export * from "./catalog.js";