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>

test/fixtures/alexa-docs/alexa-brightnesscontroller/SetBrightness.response.json

@@ -0,0 +1,30 @@
+{
+  "event": {
+    "header": {
+      "namespace": "Alexa",
+      "name": "Response",
+      "messageId": "Unique identifier, preferably a version 4 UUID",
+      "correlationToken": "Opaque correlation token that matches the request",
+      "payloadVersion": "3"
+    },
+    "endpoint": {
+      "scope": {
+        "type": "BearerToken",
+        "token": "OAuth2.0 bearer token"
+      },
+      "endpointId": "Endpoint ID"
+    },
+    "payload": {}
+  },
+  "context": {
+    "properties": [
+      {
+        "namespace": "Alexa.BrightnessController",
+        "name": "brightness",
+        "value": 50,
+        "timeOfSample": "2017-02-03T16:20:50.52Z",
+        "uncertaintyInMilliseconds": 500
+      }
+    ]
+  }
+}