fix: remove unnecessary f-string prefixes and unused import (#2352)

- Remove f-string prefix on 7 strings with no placeholders (F541)
  in analyze.py, aggregate_benchmark.py, run_loop.py, generate_review.py
- Remove unused `os` import in quick_validate.py (F401)

Found by ruff via HUMMBL Arbiter (https://hummbl.io/audit).

skills/public/skill-creator/scripts/quick_validate.py

@@ -4,7 +4,6 @@ Quick validation script for skills - minimal version
 """
 
 import sys
-import os
 import re
 import yaml
 from pathlib import Path