style: Fix linting errors and organize imports

engine/plugins.py

@@ -38,10 +38,10 @@ def register_stages(registry):
 def _register_data_sources(registry):
     """Register Mainline data source stages."""
     try:
-        from engine.data_sources.sources import HeadlinesDataSource, PoetryDataSource
         from engine.data_sources.pipeline_introspection import (
             PipelineIntrospectionSource,
         )
+        from engine.data_sources.sources import HeadlinesDataSource, PoetryDataSource
 
         registry.register("source", HeadlinesDataSource)
         registry.register("source", PoetryDataSource)
@@ -60,13 +60,6 @@ def _register_data_sources(registry):
 def _register_effects(registry):
     """Register Mainline effect stages."""
     try:
-        # Register effects
-        from sideline.effects import EffectRegistry
-        from sideline.effects.registry import get_registry
-
-        # Get the global effect registry instance
-        effect_registry = get_registry()
-
         # Note: EffectRegistry stores effect instances, not classes
         # For now, skip effect registration since it requires more refactoring
         logger.info("Effect registration skipped (requires effect refactoring)")