Fix Ruff lint and formatting failures on main

[waqasm86]

Summary

This follow-up applies the lint, whitespace, and Ruff formatting corrections that were committed after PR #4 had already been merged.

Fixes

• removes unused imports;
• removes unnecessary read-mode arguments;
• removes trailing whitespace;
• applies canonical Ruff formatting.

Validation

• python -m ruff check .
• python -m ruff format --check .
• python -m compileall -q src
• python -m mypy src
• CPU-safe pytest suite: 184 passed, 6 deselected
• canonical notebook policy checks
• public delivery safety scan
• wheel and source-distribution build
• git diff --check

This changes code quality and formatting only. It does not expand CommGuard's scientific claims.

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