fix(acms): move ContextAssemblyPipeline import to module level in step defs

Per project import rules, all imports must appear at the top of the file.
The ContextAssemblyPipeline import was inside the @then step function body;
moved it to the module-level imports section alongside other production-code
imports.

ISSUES CLOSED: #10027

features/steps/execute_phase_context_assembler_coverage_steps.py

@@ -19,6 +19,9 @@ from unittest.mock import MagicMock, patch
 from behave import given, then, when
 from behave.runner import Context
 
+from cleveragents.application.services.acms_pipeline import (
+    ContextAssemblyPipeline,
+)
 from cleveragents.application.services.execute_phase_context_assembler import (
     ACMSExecutePhaseContextAssembler,
 )
@@ -162,10 +165,6 @@ def step_epcov_explicit_pipeline(context: Context) -> None:
 @then("epcov the internal pipeline should be a ContextAssemblyPipeline")
 def step_epcov_default_pipeline_is_context_assembly(context: Context) -> None:
 
-    from cleveragents.application.services.acms_pipeline import (
-        ContextAssemblyPipeline,
-    )
-
     assert isinstance(
         context.epcov_assembler._pipeline,
         ContextAssemblyPipeline,