fixed cartesia collect audio from stream

lib/synth-audio.js

@@ -1329,7 +1329,7 @@ const synthCartesia = async(logger, {
   try {
     const client = new CartesiaClient({ apiKey: api_key });
     const sampleRate = 48000;
-    const mp3 = await client.tts.bytes({
+    const mp3Stream = await client.tts.bytes({
       modelId: model_id,
       transcript: text,
       voice: {
@@ -1363,8 +1363,16 @@ const synthCartesia = async(logger, {
         sampleRate
       },
     });
+
+    // bytes() returns a ReadableStream - collect all chunks
+    const chunks = [];
+    for await (const chunk of mp3Stream) {
+      chunks.push(chunk);
+    }
+    const audioBuffer = Buffer.concat(chunks);
+
     return {
-      audioContent: Buffer.from(mp3),
+      audioContent: audioBuffer,
       extension: 'mp3',
       sampleRate
     };

test/synth.js

@@ -716,7 +716,7 @@ test('Cartesia speech synth tests', async(t) => {
       text,
       renderForCaching: true
     });
-    t.ok(!opts.servedFromCache, `successfully playht eleven audio to ${opts.filePath}`);
+    t.ok(!opts.servedFromCache, `successfully cartesia eleven audio to ${opts.filePath}`);
 
   } catch (err) {
     console.error(JSON.stringify(err));