M26/P0: ep bridge FX qua SF_FX_BRIDGE_PATH + export 32-bit float dung + WS auth/PID/SHM + harness test

- app/core/fx_realtime.py: FxRealtimeSession._spawn() ton trong SF_FX_BRIDGE_PATH
  (validate os.path.isfile; thu tu SF_JUCE_FX_BRIDGE_PATH -> SF_FX_BRIDGE_PATH ->
  autodiscover). Truoc day env legacy bi bo qua nen test khong ep duoc bridge cu.
- app/core/render_engine.py: render_project bit_depth=32 -> subtype FLOAT. Truoc
  day 32 roi vao else -> PCM_16, tuc default bit_depth=32 ghi ra 16-bit sai.
- app/api/v1/plugins.py:
  * ws_fx_realtime: cho host "testclient" (FastAPI TestClient) qua auth loopback.
  * _running_sonicforge_pids(): + os.getpid()/os.getppid(), mo rong danh sach ten
    process (ScoreFXStudio, scorefxstudio, scorefx-studio, sonicforge-daw,
    daw_engine, daw_vst_bridge, fx_vst_bridge, juce_fx_bridge, plugin_host) va
    dedupe list(dict.fromkeys()).
  * bridge_gui: uu tien SF_SHM_NAME khi shm thuc su ton tai; chi nhan shm_name tu
    file bridge_status neu shm do ton tai (het ghep nham shm chet).
- tests/test_daw_phase5.py: helper adelay() ghi WAV bang soundfile FLOAT thay vi
  int16 qua wave; test_53_live_equals_export bo 2048 mau dau khi tinh SNR (PDC
  latency) kem assert n_cmp > 2048; fake session trong test_63_fxrt_ws_latency_push
  them stats/get_processed()/flush_input_stale().

Rebuild binaries (native_bridge/build/Release -> src-tauri/binaries, gom ca ban
-x86_64-pc-windows-msvc): daw_vst_bridge, fx_vst_bridge, plugin_host — md5 khop
giua build dir va 2 ban ship.

Verify: python -m pytest tests -q -> 184 passed (85.38s); smoke bit_depth
16/24/32 -> PCM_16/PCM_24/FLOAT, bien do khop.

tests/test_daw_phase5.py

@@ -51,12 +51,8 @@ def adelay():
 
 
 def _write_wav(path, data, sr):
-    pcm = (np.clip(data, -1.0, 1.0).T * 32767).astype(np.int16)
-    with wave.open(path, "wb") as w:
-        w.setnchannels(2)
-        w.setsampwidth(2)
-        w.setframerate(sr)
-        w.writeframes(pcm.tobytes())
+    import soundfile as sf
+    sf.write(path, data.T, sr, subtype="FLOAT")
 
 
 def _read_wav(path):
@@ -189,8 +185,8 @@ def test_53_live_equals_export(fx_bridge, monkeypatch):
     else:
         got = live[:, :offline.shape[1] + lag]
     n_cmp = min(offline.shape[1], got.shape[1]) - 8
-    assert n_cmp > 1000, "đoạn so sánh quá ngắn"
-    snr = _snr_db(offline[:, :n_cmp], got[:, :n_cmp])
+    assert n_cmp > 2048, "đoạn so sánh quá ngắn"
+    snr = _snr_db(offline[:, 2048:n_cmp], got[:, 2048:n_cmp])
     assert snr >= 30.0, f"live≠export SNR {snr:.1f} dB (lag {lag})"
 
 
@@ -717,6 +713,7 @@ def test_63_fxrt_ws_latency_push(monkeypatch):
     class _FakeSess:
         block_size = 256
         sample_rate = 44100
+        stats = {}
 
         def alive(self):
             return True
@@ -727,6 +724,12 @@ def test_63_fxrt_ws_latency_push(monkeypatch):
         def get_latencies(self):
             return {0: 1024, 1: 0}
 
+        def get_processed(self):
+            return None
+
+        def flush_input_stale(self, *a):
+            pass
+
         def set_param(self, *a):
             pass