fix(tts): scan WAV data chunk instead of hardcoding 44-byte header offset

WAV files with extra chunks (LIST, fact, bext) had metadata bytes fed
into AudioTrack as PCM, causing distorted playback. Now walks the chunk
structure to find the actual "data" chunk start.

Author: Siddhesh2377

examples/android/RunAnywhereAI/app/src/main/java/com/runanywhere/runanywhereai/presentation/tts/TextToSpeechViewModel.kt

@@ -509,25 +509,42 @@ class TextToSpeechViewModel(
                         audioData[3] == 'F'.code.toByte()
 
                     val sampleRate: Int
-                    val headerSize: Int
+                    val pcmOffset: Int
 
                     if (isWav) {
                         // WAV header: bytes 24-27 = sample rate (little-endian uint32)
                         sampleRate = (audioData[24].toInt() and 0xFF) or
                             ((audioData[25].toInt() and 0xFF) shl 8) or
                             ((audioData[26].toInt() and 0xFF) shl 16) or
                             ((audioData[27].toInt() and 0xFF) shl 24)
-                        headerSize = 44
-                        Timber.i("WAV header: sampleRate=$sampleRate")
+
+                        // Scan for the "data" chunk — WAV files can have extra
+                        // chunks (LIST, fact, bext, …) before the PCM payload.
+                        var offset = 12 // skip RIFF header (12 bytes)
+                        var dataStart = -1
+                        while (offset + 8 <= audioData.size) {
+                            val chunkId = String(audioData, offset, 4, Charsets.US_ASCII)
+                            val chunkSize = (audioData[offset + 4].toInt() and 0xFF) or
+                                ((audioData[offset + 5].toInt() and 0xFF) shl 8) or
+                                ((audioData[offset + 6].toInt() and 0xFF) shl 16) or
+                                ((audioData[offset + 7].toInt() and 0xFF) shl 24)
+                            if (chunkId == "data") {
+                                dataStart = offset + 8
+                                break
+                            }
+                            offset += 8 + chunkSize
+                        }
+                        pcmOffset = if (dataStart > 0) dataStart else 44 // fallback for malformed files
+                        Timber.i("WAV header: sampleRate=$sampleRate, pcmOffset=$pcmOffset")
                     } else {
                         sampleRate = _uiState.value.sampleRate ?: 22050
-                        headerSize = 0
+                        pcmOffset = 0
                     }
 
                     val channelConfig = AudioFormat.CHANNEL_OUT_MONO
                     val audioFormat = AudioFormat.ENCODING_PCM_16BIT
 
-                    val pcmData = audioData.copyOfRange(headerSize, audioData.size)
+                    val pcmData = audioData.copyOfRange(pcmOffset, audioData.size)
 
                     val bufferSize = AudioTrack.getMinBufferSize(sampleRate, channelConfig, audioFormat)