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_reflexion.py

@@ -5,6 +5,7 @@ Tests error learning and prevention functionality.
 """
 
 import pytest
+
 from superclaude.pm_agent.reflexion import ReflexionPattern
 
 
@@ -165,7 +166,7 @@ def test_reflexion_with_real_exception():
 
     try:
         # Simulate an operation that fails
-        result = 10 / 0
+        _ = 10 / 0  # noqa: F841
     except ZeroDivisionError as e:
         # Record the error
         error_info = {