feat(audio): add media stream output

[deltakosh]

Summary

• expose an opt-in post-master MediaStream for recording and WebRTC without changing speaker output
• add standalone, idempotent disposal that unregisters engine cleanup and stops owned tracks
• document the public API and cover wiring, manual disposal, engine disposal, and offline rejection

Validation

• pnpm run lint
• pnpm exec vitest run --project unit tests/lite/unit/audio/media-stream-output.test.ts (4 passed)
• pnpm test (bundle-size gate passed; 427 parity tests passed; only the known unrelated scenes 47, 104, 105, 106, and 265 failed)
• Chromium smoke check against the built package: one live audio track is created and becomes ended after disposal

[bjsplat]

API Changes

API Extractor detected public API changes for @babylonjs/lite.

No removed public API lines were detected; this appears to be additive.

API Extractor diff

diff --git a/home/vsts/work/1/s/test-results/api-report/target/temp/babylon-lite.api.md b/home/vsts/work/1/s/test-results/api-report/current/temp/babylon-lite.api.md
index a6130e19..089f7ff3 100644
--- a/home/vsts/work/1/s/test-results/api-report/target/temp/babylon-lite.api.md
+++ b/home/vsts/work/1/s/test-results/api-report/current/temp/babylon-lite.api.md
@@ -470,6 +470,11 @@ export interface AudioEngine {
     readonly state: AudioEngineState;
 }
 
+// @public
+export interface AudioEngineMediaStream {
+    readonly stream: MediaStream;
+}
+
 // @public
 export interface AudioEngineOptions {
     audioContext?: BaseAudioContext;
@@ -1155,6 +1160,9 @@ export function createAudioBusAsync(engine: AudioEngine, name: string, options?:
 // @public
 export function createAudioEngineAsync(options?: AudioEngineOptions): Promise<AudioEngine>;
 
+// @public
+export function createAudioEngineMediaStream(engine: AudioEngine): AudioEngineMediaStream;
+
 // @public
 export function createAudioVisualizer(host: AudioGraphHost, canvas: HTMLCanvasElement, options?: AudioVisualizerOptions): AudioVisualizer;
 
@@ -1898,6 +1906,9 @@ export function disposeAudioBus(bus: AudioBus): void;
 // @public
 export function disposeAudioEngine(engine: AudioEngine): void;
 
+// @public
+export function disposeAudioEngineMediaStream(output: AudioEngineMediaStream): void;
+
 // @public
 export function disposeAudioVisualizer(viz: AudioVisualizer): void;

[bjsplat]

Lite Playground - Static Site

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_{Build 20260719.1 - merge @ 0311fa6}

[Copilot]

Pull request overview

Adds an opt-in MediaStream “tap” for Babylon Lite’s AudioEngine final (post-master) mix so consumers can record or forward audio (e.g., WebRTC) without changing normal speaker output, with explicit idempotent disposal and engine-owned cleanup.

Changes:

• Introduces createAudioEngineMediaStream / disposeAudioEngineMediaStream and the AudioEngineMediaStream handle.
• Extends the unit WebAudio mock to support createMediaStreamDestination() and a mock destination node.
• Adds unit tests and updates architecture docs + public exports for the new API.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/lite/unit/audio/web-audio-mock.ts	Adds mock createMediaStreamDestination() and MockMediaStreamAudioDestinationNode support for unit testing.
tests/lite/unit/audio/media-stream-output.test.ts	New unit tests covering wiring, idempotent disposal, engine-disposal cleanup, and offline-context rejection.
packages/babylon-lite/src/index.ts	Re-exports the new media-stream output API at the package root.
packages/babylon-lite/src/audio/media-stream-output.ts	Implements the MediaStream output tap and safe, idempotent disposal behavior.
packages/babylon-lite/src/audio/index.ts	Re-exports the new API from the audio barrel.
docs/lite/architecture/41-audio-engine.md	Documents the new Lite-only media-stream output feature and updates the audio module manifest.

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[bjsplat]

Lab - Static Site

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_{Build 20260719.1 - merge @ 0311fa6}