fix(tests): resolve pre-existing AmbiguousStep collisions in step definitions

Rename step texts to avoid case-sensitive conflicts between different step modules:

- edge_case_plan_steps.py: 'a Pydantic validation error' -> 'an Edge Case Pydantic validation error'
- plan_executor_coverage_boost_steps.py: 'the rollback result should be False' -> 'the executor rollback result should be False'
- plan_explain_steps.py: 'the json output should be valid json' -> 'the plan explain json output should be valid'
- plan_model_steps.py: 'I create a plan in strategize phase' -> 'I create a PlanModel in strategize phase'
- project_repository_steps.py: 'the remove result should be False' -> 'the project repo remove result should be False'
- service_retry_wiring_steps.py: 'I create a ServiceRetryWiring from those Settings' -> 'I create a ServiceRetryWiring from those retry Settings'
- session_model_steps.py: 'I get the session CLI dict' -> 'I get the session model CLI dict'

These pre-existing bugs prevented all behave tests from loading.

features/steps/edge_case_plan_steps.py

@@ -755,7 +755,7 @@ def step_try_create_plan_empty_desc(context: Context) -> None:
         context.pydantic_error = exc
 
 
-@then("a Pydantic validation error should be raised")
+@then("an Edge Case Pydantic validation error should be raised")
 def step_check_pydantic_error(context: Context) -> None:
     assert context.pydantic_error is not None, "Expected a Pydantic validation error"