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

native_bridge/src/FxGuiServer.cpp

@@ -33,8 +33,12 @@
 #include <thread>
 #include <vector>
 
-// sheredom/json.h (vendored with the VST3 SDK) — same include as RenderFxJob.cpp.
+// sheredom/json.h (public domain) — vendored copy; SDK copy as fallback.
+#if __has_include("sheredom_json.h")
+#include "sheredom_json.h"
+#elif __has_include("vst3sdk/public.sdk/source/vst/moduleinfo/json.h")
 #include "vst3sdk/public.sdk/source/vst/moduleinfo/json.h"
+#endif
 
 namespace {