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/compat/ActionMapping.js

@@ -0,0 +1,45 @@
+import { DeclarationError } from "../registry/types.js";
+/**
+ * A semantics action mapping of 1.x: the phrases "open", "close", "raise", "lower" for one directive of the
+ * capability it is added to.
+ *
+ *   toggle.addActionMapping(new ActionMapping([AlexaActions.Close], "TurnOff"));
+ *   lift.addActionMapping(new ActionMapping([AlexaActions.Open], "SetRangeValue", { rangeValue: 100 }));
+ */
+export class ActionMapping {
+    /**
+     * directivePayload is the payload object of the directive (alexa-discovery-objects.html, "ActionMappings object").
+     * 1.x took a string and put it into discovery as one. A string that holds a JSON object is parsed; any other
+     * string throws a DeclarationError.
+     */
+    constructor(actions, directiveName, directivePayload) {
+        this.type = "ActionsToDirective";
+        this.actions = actions;
+        this.directive = { name: directiveName };
+        if (typeof directivePayload === "string") {
+            if (directivePayload === "")
+                return;
+            this.directive.payload = objectIn(directivePayload, directiveName);
+            this.deprecation = `the payload of the action mapping for ${directiveName} is a JSON string, pass the object`;
+        }
+        else if (directivePayload) {
+            this.directive.payload = directivePayload;
+        }
+    }
+    toJSON() {
+        return { "@type": this.type, actions: this.actions, directive: this.directive };
+    }
+}
+function objectIn(text, directiveName) {
+    let value;
+    try {
+        value = JSON.parse(text);
+    }
+    catch {
+        value = undefined;
+    }
+    if (typeof value !== "object" || value === null || Array.isArray(value)) {
+        throw new DeclarationError({}, `the payload of the action mapping for ${directiveName} is an object, got the string ${JSON.stringify(text)}`);
+    }
+    return value;
+}