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_cli_install.py

@@ -4,8 +4,6 @@ Unit tests for CLI install command
 Tests the command installation functionality.
 """
 
-import pytest
-from pathlib import Path
 from superclaude.cli.install_commands import (
     install_commands,
     list_available_commands,
@@ -172,7 +170,6 @@ def test_cli_integration():
     This tests that the CLI main.py can successfully import the functions
     """
     from superclaude.cli.install_commands import (
-        install_commands,
         list_available_commands,
     )