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-temperaturesensor/discovery.json

@@ -0,0 +1,91 @@
+{
+  "event": {
+    "header": {
+      "namespace": "Alexa.Discovery",
+      "name": "Discover.Response",
+      "payloadVersion": "3",
+      "messageId": "Unique identifier, preferably a version 4 UUID"
+    },
+    "payload": {
+      "endpoints": [
+        {
+          "endpointId": "Unique ID of the endpoint",
+          "manufacturerName": "Manufacturer of the endpoint",
+          "description": "Smart Thermostat by Thermostat Maker",
+          "friendlyName": "Hallway Thermostat",
+          "displayCategories": [
+            "THERMOSTAT",
+            "TEMPERATURE_SENSOR"
+          ],
+          "cookie": {},
+          "capabilities": [
+            {
+              "type": "AlexaInterface",
+              "interface": "Alexa.TemperatureSensor",
+              "version": "3",
+              "properties": {
+                "supported": [
+                  {
+                    "name": "temperature"
+                  }
+                ],
+                "proactivelyReported": true,
+                "retrievable": true
+              }
+            },
+            {
+              "type": "AlexaInterface",
+              "interface": "Alexa.ThermostatController",
+              "version": "3.1",
+              "properties": {
+                "supported": [
+                  {
+                    "name": "targetSetpoint"
+                  },
+                  {
+                    "name": "lowerSetpoint"
+                  },
+                  {
+                    "name": "upperSetpoint"
+                  },
+                  {
+                    "name": "thermostatMode"
+                  }
+                ],
+                "proactivelyReported": true,
+                "retrievable": true
+              },
+              "configuration": {
+                "supportedModes": [
+                  "HEAT",
+                  "COOL",
+                  "AUTO"
+                ],
+                "supportsScheduling": false
+              }
+            },
+            {
+              "type": "AlexaInterface",
+              "interface": "Alexa.EndpointHealth",
+              "version": "3",
+              "properties": {
+                "supported": [
+                  {
+                    "name": "connectivity"
+                  }
+                ],
+                "proactivelyReported": true,
+                "retrievable": true
+              }
+            },
+            {
+              "type": "AlexaInterface",
+              "interface": "Alexa",
+              "version": "3"
+            }
+          ]
+        }
+      ]
+    }
+  }
+}