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/test_llm_capabilities.py

@@ -108,7 +108,7 @@ def main():
     if valid_results:
         total = sum(valid_results)
         avg = total / len(valid_results)
-        print(f"\n📊 Benchmark Summary:")
+        print("\n📊 Benchmark Summary:")
         print(f"Total Time for 4 tasks: {total:.2f}s")
         print(f"Average Time: {avg:.2f}s per task")