fix: Update imports to use engine.pipeline instead of engine.pipeline.core

The old engine/pipeline/core.py file was removed as part of the Sideline/Mainline split.
All imports that referenced engine.pipeline.core have been updated to use engine.pipeline
which re-exports from sideline.pipeline.core.

This ensures consistency and avoids duplicate DataType enum instances.

engine/sensors/__init__.py

@@ -25,7 +25,7 @@ from dataclasses import dataclass
 from typing import TYPE_CHECKING, Any
 
 if TYPE_CHECKING:
-    from engine.pipeline.core import PipelineContext
+    from engine.pipeline import PipelineContext
 
 
 @dataclass
@@ -166,13 +166,13 @@ class SensorStage:
 
     @property
     def inlet_types(self) -> set:
-        from engine.pipeline.core import DataType
+        from engine.pipeline import DataType
 
         return {DataType.ANY}
 
     @property
     def outlet_types(self) -> set:
-        from engine.pipeline.core import DataType
+        from engine.pipeline import DataType
 
         return {DataType.ANY}