fix: resolve ruff lint errors in benchmark suite

Remove unused imports (shutil, string, datetime, os, yaml, time,
SCALE_CONFIGS) and unused variable assignments in timing-only calls.

tests/benchmarks/test_memory_profile.py

@@ -8,7 +8,6 @@ Targets the highest-risk code paths:
   - Layer1.generate() (fetches all drawers)
 """
 
-import time
 import tracemalloc
 
 import pytest