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/chunk_statistics.py

@@ -6,7 +6,6 @@ Generates a comprehensive report of each chunk's content.
 
 import json
 import os
-import sys
 
 UUID = "384b0ff44aaaa1f1"
 BASE_DIR = f"output/{UUID}"
@@ -107,7 +106,7 @@ def print_summary(chunks):
         1 for c in chunks if not c["has_speech"] and not c["has_faces"]
     )
 
-    print(f"\n📊 Overview:")
+    print("\n📊 Overview:")
     print(f"   Total chunks:        {len(chunks)}")
     print(
         f"   Chunks with speech:  {total_speech_chunks} ({total_speech_chunks / len(chunks) * 100:.0f}%)"
@@ -125,7 +124,7 @@ def print_summary(chunks):
     print(f"   Total face frames:   {total_faces}")
 
     # Combination breakdown
-    print(f"\n🎯 ASR/Face Combination Breakdown:")
+    print("\n🎯 ASR/Face Combination Breakdown:")
 
     combos = {}
     for c in chunks:
@@ -148,7 +147,7 @@ def print_summary(chunks):
         )
 
     # Top chunks by activity
-    print(f"\n🔥 Top 10 Most Active Chunks (by ASR+Faces):")
+    print("\n🔥 Top 10 Most Active Chunks (by ASR+Faces):")
     scored_chunks = []
     for c in chunks:
         score = c["asr_count"] + c["face_count"]
@@ -164,7 +163,7 @@ def print_summary(chunks):
         )
 
     # Stamp scene chunk
-    print(f"\n🔍 Special Interest Chunks:")
+    print("\n🔍 Special Interest Chunks:")
     for c in chunks:
         # Stamp scene around 5730s
         if c["start"] <= 5730 <= c["end"]: