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/generate_chunk_summaries.py

@@ -252,7 +252,6 @@ Summary: [2-3 sentence detailed summary connecting to scene]"""
 
 def parse_5w1h_summary(result_text):
     """Parse 5W1H and summary from LLM response"""
-    import re
 
     data = {
         "who": "",
@@ -314,7 +313,6 @@ def update_chunk_summary(
     uuid=None,
 ):
     """Update chunk summary, 5W1H, identity, and visual in database"""
-    import json
 
     conn = psycopg2.connect(**DB_CONFIG)
     cur = conn.cursor()