perf: reuse GCC-PHAT TDOA; skip 16 kHz AudioNormalizer

Delay-and-Sum still uses the tutorial STFT/cov/GCC-PHAT/DelaySum/ISTFT
path. TDOA is refreshed every BEAMFORM_TDOA_EVERY hops (default 5).

tests/test_audio_cleanup.py

@@ -57,6 +57,32 @@ def test_beamform_loads_delaysum_module():
     assert "beamform" in c.backend
 
 
+def test_beamform_skips_normalizer_at_native_rate():
+    c = AudioCleaner(mode="off", beamform="force", sample_rate=16000)
+    assert c._normalizer is None
+
+
+def test_tdoa_reused_across_hops():
+    c = AudioCleaner(mode="off", beamform="force", tdoa_every=5)
+    assert c._gccphat is not None
+    calls = {"n": 0}
+    orig = c._gccphat
+
+    def wrapped(*a, **k):
+        calls["n"] += 1
+        return orig(*a, **k)
+
+    c._gccphat = wrapped
+    hop = 3200
+    t = np.arange(hop)
+    ch0 = (np.sin(2 * np.pi * 440 * t / 16000) * 8000).astype(np.int16)
+    stereo = np.stack([ch0, np.roll(ch0, 2)], axis=1)
+    for _ in range(3):
+        out = c.process(stereo)
+        assert out.shape == (hop,)
+    assert calls["n"] == 1
+
+
 def test_process_records_last_dt_ms():
     c = AudioCleaner(mode="off", beamform="off")
     hop = 3200