registry: Speaker, StepSpeaker, EqualizerController, PlaybackController, PlaybackStateReporter, InputController, ChannelController

Seven descriptors written from their pages replace seven stubs. All are version 3; 1.5.2 announced Speaker,
StepSpeaker, EqualizerController and PlaybackStateReporter as version 1, and all but ChannelController without
a property. StepSpeaker has no properties object in discovery and PlaybackController one without fields, next
to supportedOperations; a directive for an operation the device did not list is answered with
INVALID_DIRECTIVE. The equalizer declares bands, modes or both under "configurations", a TV its inputs from
the 61 names of the page.

Not described: the lineup of ChannelController, whose discovery example the page folds away. The discovery
examples of InputController spell one key "friendNames"; the fixtures have friendlyNames, as its table does.
62 examples of the six pages are saved as fixtures. 241 tests pass, 215 before.

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

test/fixtures/alexa-docs/alexa-channelcontroller/discovery-addOrUpdateReport.json

@@ -0,0 +1,69 @@
+{
+  "event": {
+    "header": {
+      "namespace": "Alexa.Discovery",
+      "name": "AddOrUpdateReport",
+      "payloadVersion": "3",
+      "messageId": "Unique identifier, preferably a version 4 UUID"
+    },
+    "payload": {
+      "endpoints": [
+        {
+          "endpointId": "unique ID of the new endpoint",
+          "manufacturerName": "Manufacturer of the endpoint",
+          "description": "Description to be shown in the Alexa app",
+          "friendlyName": "Living Room TV",
+          "displayCategories": [
+            "TV"
+          ],
+          "additionalAttributes": {
+            "manufacturer": "Manufacturer of the endpoint",
+            "model": "Model of the device",
+            "serialNumber": "Serial number of the device",
+            "firmwareVersion": "Firmware version of the device",
+            "softwareVersion": "Software version of the device"
+          },
+          "capabilities": [
+            {
+              "type": "AlexaInterface",
+              "interface": "Alexa.ChannelController",
+              "version": "3",
+              "properties": {
+                "supported": [
+                  {
+                    "name": "channel"
+                  }
+                ],
+                "proactivelyReported": true,
+                "retrievable": true
+              }
+            },
+            {
+              "type": "AlexaInterface",
+              "interface": "Alexa.EndpointHealth",
+              "version": "3.1",
+              "properties": {
+                "supported": [
+                  {
+                    "name": "connectivity"
+                  }
+                ],
+                "proactivelyReported": true,
+                "retrievable": true
+              }
+            },
+            {
+              "type": "AlexaInterface",
+              "interface": "Alexa",
+              "version": "3"
+            }
+          ]
+        }
+      ],
+      "scope": {
+        "type": "BearerToken",
+        "token": "access-token-from-Amazon"
+      }
+    }
+  }
+}