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_benchmark_summary.py

@@ -148,7 +148,7 @@ def generate_summary_report():
         fastest_scheme = fastest.get('file_info', {}).get('scheme_id', 'unknown')
         fastest_time = fastest.get('metrics', {}).get('processing_time_seconds', 0)
         
-        lines.append(f"### Performance Comparison")
+        lines.append("### Performance Comparison")
         lines.append("")
         lines.append(f"- **Fastest Scheme**: {fastest_scheme} ({fastest_time:.1f}s)")
         
@@ -169,7 +169,7 @@ def generate_summary_report():
         lines.append("")
     
     if failed_tests:
-        lines.append(f"### Failed Tests")
+        lines.append("### Failed Tests")
         lines.append("")
         for result in failed_tests:
             scheme_id = result.get('file_info', {}).get('scheme_id', 'unknown')
@@ -178,8 +178,8 @@ def generate_summary_report():
             
             if 'MPS' in error_msg:
                 lines.append(f"- **{scheme_id} ({scheme_name})**: MPS backend compatibility issue")
-                lines.append(f"  - PyTorch SparseMPS backend does not support `_sparse_coo_tensor_with_dims_and_tensors`")
-                lines.append(f"  - OpenAI whisper requires this operation for MPS device")
+                lines.append("  - PyTorch SparseMPS backend does not support `_sparse_coo_tensor_with_dims_and_tensors`")
+                lines.append("  - OpenAI whisper requires this operation for MPS device")
         
         lines.append("")