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/scan_keyframes_opencv.py

@@ -6,7 +6,6 @@ Batch Scan Keyframes for SMALL red stamps
 import cv2
 import numpy as np
 import os
-import json
 
 UUID = "384b0ff44aaaa1f1"
 BASE_DIR = f"output/{UUID}/florence2_results"
@@ -93,4 +92,4 @@ for frame_name in FRAMES:
         res_name = f"result_opencv_{frame_name}"
         cv2.imwrite(os.path.join(BASE_DIR, res_name), img)
     else:
-        print(f"   ❌ No small stamps found.")
+        print("   ❌ No small stamps found.")