chore: remove unused imports and dead code

sync_audio_test.py

@@ -13,7 +13,7 @@ Run: make ast  or  .venv/bin/python sync_audio_test.py --config config.toml
 """
 
 from __future__ import annotations
-import os, sys, math, argparse, pathlib
+import os, sys, math, argparse
 import numpy as np
 
 # allow tomllib (py3.11+) with tomli fallback
@@ -31,12 +31,6 @@ except ImportError as e:
     print(e, file=sys.stderr)
     sys.exit(1)
 
-try:
-    import soundfile as sf
-    HAS_SF = True
-except ImportError:
-    HAS_SF = False
-
 try:
     import sounddevice as sd
     HAS_SD = True
@@ -152,15 +146,9 @@ class SyncWindow(QtWidgets.QMainWindow):
 
         # xcorr display — corr is already fftshifted
         N = len(self.corr)
-        # lags in seconds for display
-        total = len(self.a) + len(self.b) - 1
-        n_pow2 = N
         # shifted lags: -N//2 .. N//2-1
         self.corr_lags = np.arange(N) - N//2
         self.corr_lags_sec = self.corr_lags / sr
-        # find peak index in raw (unshifted) for decimation
-        peak_raw_idx = int(np.argmax(np.abs(self.corr)))  # this is fftshifted, peak near center
-        # for decimation we need the index in the shifted array
 
         central = QtWidgets.QWidget()
         self.setCentralWidget(central)