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>

src/registry/interfaces/ChannelController.ts

@@ -0,0 +1,42 @@
+import { s } from "../schema.js";
+import { defineInterface } from "../types.js";
+
+// None of the fields is required, a channel has one of them at least
+const channel = s.object({
+  /** "256", "13.1" */
+  number: s.optional(s.string()),
+  callSign: s.optional(s.string()),
+  affiliateCallSign: s.optional(s.string()),
+  uri: s.optional(s.string()),
+});
+
+/**
+ * The channel of a TV. ChangeChannel names the channel by one or more of number, callSign, affiliateCallSign and
+ * uri, or by channelMetadata.name alone. The lineup of a TV provider is not described: the page folds the discovery
+ * example that has one.
+ */
+export const ChannelController = defineInterface({
+  namespace: "Alexa.ChannelController",
+  version: "3",
+  doc: "https://developer.amazon.com/docs/alexaplus/device-apis/alexa-channelcontroller.html",
+  kind: "controller",
+  tier: 2,
+  instanced: false,
+  properties: {
+    channel: { name: "channel", value: channel },
+  },
+  directives: {
+    ChangeChannel: {
+      name: "ChangeChannel",
+      payload: s.object({
+        channel: s.optional(channel),
+        channelMetadata: s.optional(s.object({ name: s.optional(s.string()), image: s.optional(s.string()) })),
+      }),
+    },
+    SkipChannels: {
+      name: "SkipChannels",
+      payload: s.object({ channelCount: s.number({ integer: true }) }),
+      note: "above 0 up, below 0 down",
+    },
+  },
+});