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/tmdb_cast_fetcher.py

@@ -149,9 +149,9 @@ def main():
                 print(f"     ✅ Saved: {local_path.name}")
                 results.append({"name": name, "role": role, "image": str(local_path)})
             else:
-                print(f"     ⚠️ Failed to download")
+                print("     ⚠️ Failed to download")
         else:
-            print(f"     ⚠️ No profile image available")
+            print("     ⚠️ No profile image available")
 
     # Save metadata
     meta_path = movie_dir / "cast_data.json"