cleanup: remove dead code and duplicate docs

- Remove session-ses_2f27.md (161KB raw session log)
- Remove 49 ROOT_* duplicate files across REFERENCE/
- Remove 14 duplicate files between REFERENCE/ root and history/
- Remove asr_legacy.rs (dead code, replaced by asr.rs)
- Remove src/core/worker/ (duplicate JobWorker)
- Remove src/core/layers/ (empty directory)
- Remove 4 .bak files in src/
- Remove 7 dead private methods in worker/processor.rs
- Remove backup directory from git tracking

scripts/sound_event_detector.py

@@ -26,7 +26,7 @@ def detect_impulse_sounds(audio_path, threshold_multiplier=1.5):
     # 載入音頻 (Mono, 22050Hz)
     y, sr = librosa.load(audio_path, sr=22050)
 
-    print(f"📊 Analyzing energy envelope...")
+    print("📊 Analyzing energy envelope...")
     # 1. 計算 RMS 能量 (以 0.05秒 為一幀)
     frame_length = int(0.05 * sr)
     hop_length = int(0.02 * sr)