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/asrx_self/vad.py

@@ -9,7 +9,6 @@ VAD (Voice Activity Detection) - 語音活動檢測
 """
 
 import torch
-import numpy as np
 
 
 def load_vad_model():
@@ -143,7 +142,7 @@ if __name__ == "__main__":
     print(f"[VAD] Processing: {audio_path}")
     segments, wav, sr = extract_speech_segments(audio_path, model, utils)
 
-    print(f"\n[VAD] Results:")
+    print("\n[VAD] Results:")
     print(f"  Sample rate: {sr} Hz")
     print(f"  Speech segments: {len(segments)}")
     print(f"  Total duration: {len(wav) / sr:.2f}s")
@@ -153,7 +152,7 @@ if __name__ == "__main__":
         f"  Total speech: {total_speech:.2f}s ({total_speech / (len(wav) / sr) * 100:.1f}%)"
     )
 
-    print(f"\n[VAD] Segments:")
+    print("\n[VAD] Segments:")
     for i, (start, end) in enumerate(segments[:10]):
         print(f"  {i + 1:3d}. {start:6.2f}s - {end:6.2f}s ({end - start:5.2f}s)")