Normalize Linux audio pipeline to lossless Float32 (skill: lossless-audio-compliance)

- native bridge WAV writers: 16-bit PCM truncation -> IEEE Float32 (fmt 3, bit-exact)
- vendor sheredom_json.h (vst3sdk 3.8.1 lacks moduleinfo/json.h)
- Dockerfile: drop nonexistent sfizz tag v1.2.3
- Python sf.write -> subtype=FLOAT everywhere
- resample_poly -> kaiser(16) window (>=130dB stopband)
- audio_editor._write_wav_lossless(): FLOAT passthrough, TPDF dither only for
  8/16/24-bit final exports
- app.jsx WAV encoders: Float32 default, TPDF dither for integer depths, fix 24-bit
- tests: lossless compliance gate (null test < -140dBFS, float32 format) 9/9 pass
- TASKS_WINDOWS_AUDIO_NORMALIZE.md: Windows-side remaining tasks

app/core/audio_editor.py

@@ -5,6 +5,20 @@ import soundfile as sf
 from pydub import AudioSegment
 from app.core.dsp_utils import find_nearest_zero_crossing_file, apply_micro_fade
 
+
+def _write_wav_lossless(output_path, y, sample_rate, bit_depth):
+    """Lossless WAV export (lossless-audio-compliance skill):
+    - 32-bit -> IEEE Float32, bit-exact (no dither, format 3)
+    - 8/16/24-bit -> single-stage TPDF dither ONLY at final quantization"""
+    if bit_depth == 32:
+        sf.write(output_path, y, sample_rate, subtype="FLOAT")
+        return
+    subtype = {8: "PCM_S8", 16: "PCM_16", 24: "PCM_24"}.get(bit_depth, "PCM_24")
+    rng = np.random.default_rng()
+    y = y + (rng.random(y.shape) - rng.random(y.shape))  # TPDF, [-1,1)
+    y = np.clip(y, -1.0, 1.0)  # clamp after dither — no wrap on quantization
+    sf.write(output_path, y, sample_rate, subtype=subtype)
+
 def edit_audio_file(config: dict, input_path: str, output_path: str):
     """
     Applies editing commands on the audio file based on config:
@@ -192,12 +206,8 @@ def mix_multitrack_session(tracks_meta: list, output_path: str, sample_rate: int
                 master_mix.export(temp_wav, format="wav")
                 y, sr_read = sf.read(temp_wav)
                 
-                # Xác định subtype mã hóa bit-depth
-                subtype_map = {8: "PCM_S8", 16: "PCM_16", 24: "PCM_24"}
-                selected_subtype = subtype_map.get(bit_depth, "PCM_16")
-                
-                # Ghi tệp WAV chất lượng cao
-                sf.write(output_path, y, sample_rate, subtype=selected_subtype)
+                # Ghi tệp WAV chất lượng cao (float32 / TPDF-dithered)
+                _write_wav_lossless(output_path, y, sample_rate, bit_depth)
             finally:
                 # Dọn dẹp tệp tạm (luôn thực hiện)
                 if os.path.exists(temp_wav):
@@ -254,10 +264,7 @@ def export_audio(input_path: str, output_path: str, format: str = "wav",
             sound.export(temp_wav, format="wav")
             y, sr_read = sf.read(temp_wav)
             
-            subtype_map = {8: "PCM_S8", 16: "PCM_16", 24: "PCM_24"}
-            selected_subtype = subtype_map.get(bit_depth, "PCM_16")
-            
-            sf.write(output_path, y, sample_rate, subtype=selected_subtype)
+            _write_wav_lossless(output_path, y, sample_rate, bit_depth)
         finally:
             if os.path.exists(temp_wav):
                 os.remove(temp_wav)