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>

test/helpers/fixtures.js

@@ -6,6 +6,7 @@ const fs = require("node:fs");
 const path = require("node:path");
 
 const DOCS = path.join(__dirname, "..", "fixtures", "alexa-docs");
+const ZOO = path.join(__dirname, "..", "fixtures", "zoo", "discovery.json");
 
 /** One example: doc("alexa-powercontroller", "TurnOn.directive"). */
 function doc(page, name) {
@@ -44,4 +45,15 @@ function reported(page, namespace) {
   return found.filter(({ property }) => property.namespace === namespace);
 }
 
-module.exports = { doc, examples, capabilities, reported };
+/**
+ * An endpoint of the zoo: the 22 test devices built on alex2node 1.5.2, as their discovery answer was on 2026-09-28
+ * when Alexa accepted all of them. Six had their capability JSON corrected by hand, because 1.5.2 had no way to
+ * declare it: zoo-blinds, zoo-blower, zoo-heater, zoo-lock, zoo-motion, and zoo-health-lamp-31 for its version.
+ */
+function zoo(endpointId) {
+  const endpoint = JSON.parse(fs.readFileSync(ZOO, "utf8")).find((each) => each.endpointId === endpointId);
+  if (!endpoint) throw new Error(`${endpointId} is not in the zoo`);
+  return endpoint;
+}
+
+module.exports = { doc, examples, capabilities, reported, zoo };