fix: resolve all ruff linting errors

Fixed 42 linting errors across codebase:
- Auto-fixed 35 import sorting issues (I001)
- Added unused imports to __all__ in execution/__init__.py
- Removed unused variable assignments (F841)
- Updated pyproject.toml to use [tool.ruff.lint] section

All ruff checks now pass successfully.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/unit/test_self_check.py

@@ -5,6 +5,7 @@ Tests post-implementation validation functionality.
 """
 
 import pytest
+
 from superclaude.pm_agent.self_check import SelfCheckProtocol