Prevent voice message from displaying spurious errors (#30736)

* fix: avoid to render `AudioPlayerViewModel` when `MAudioBody` is inherited

* fix: avoid `Playback.prepare` to fail when called twice

* fix: add `decoding` to playback type

* refactor: fix circular deps

* refactor: extract `MockedPlayback` from `AudioPlayerViewModel`

* test: add `MAudioBody` basic test

* test: add tests for `MVoiceMessageBody`

* fix: lint

test/unit-tests/audio/MockedPlayback.ts

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+import EventEmitter from "events";
+import { SimpleObservable } from "matrix-widget-api";
+
+import { PlaybackState } from "../../../src/audio/Playback";
+
+/**
+ * A mocked playback implementation for testing purposes.
+ * It simulates a playback with a fixed size and allows state changes.
+ */
+export class MockedPlayback extends EventEmitter {
+    public sizeBytes = 8000;
+    private waveformObservable = new SimpleObservable<number[]>();
+    public liveData = new SimpleObservable<number[]>();
+
+    public constructor(
+        public currentState: PlaybackState,
+        public durationSeconds: number,
+        public timeSeconds: number,
+    ) {
+        super();
+    }
+
+    public setState(state: PlaybackState): void {
+        this.currentState = state;
+        this.emit("update", state);
+    }
+
+    public get isPlaying(): boolean {
+        return this.currentState === PlaybackState.Playing;
+    }
+
+    public get clockInfo() {
+        return {
+            liveData: this.liveData,
+            populatePlaceholdersFrom: () => undefined,
+        };
+    }
+
+    public get waveform(): number[] {
+        return [];
+    }
+
+    public get waveformData(): SimpleObservable<number[]> {
+        return this.waveformObservable;
+    }
+
+    public prepare = jest.fn().mockResolvedValue(undefined);
+    public skipTo = jest.fn();
+    public toggle = jest.fn();
+    public destroy = jest.fn().mockResolvedValue(undefined);
+}