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/regenerate_parent_5w1h.py

@@ -185,7 +185,7 @@ def main():
             if update_parent_chunk(parent, analysis):
                 success_count += 1
         else:
-            print(f"   ❌ Failed to generate analysis")
+            print("   ❌ Failed to generate analysis")
 
     print(f"\n{'=' * 70}")
     print(