Enable Ruff B/C4/UP lint codes and fix violations

[spMohanty]

Summary

• Enable Ruff lint extensions B, C4, and UP in repository config.
• Apply and fix all new violations from these rule sets.
• Touch related code paths in core, client, tests, and benchmark areas (including Remove unused median index lookup in benchmark sorting #21 target).
• Keep behavior unchanged while removing dead code/useless expressions and tightening exception practices.

Closes #21