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/SkipChannels.response.json

@@ -0,0 +1,37 @@
+{
+  "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": {
+      "endpointId": "Endpoint ID"
+    },
+    "payload": {}
+  },
+  "context": {
+    "properties": [
+      {
+        "namespace": "Alexa.ChannelController",
+        "name": "channel",
+        "value": {
+          "number": "7",
+          "callSign": "KIRO-TV",
+          "affiliateCallSign": "KIRO"
+        },
+        "timeOfSample": "2017-02-03T16:25:50.52Z",
+        "uncertaintyInMilliseconds": 0
+      },
+      {
+        "namespace": "Alexa.PowerController",
+        "name": "powerState",
+        "value": "ON",
+        "timeOfSample": "2017-02-03T16:18:40.12Z",
+        "uncertaintyInMilliseconds": 500
+      }
+    ]
+  }
+}