feat(phase3): 清理EditPlan表冗余字段result_count

- 删除EditPlan领域模型/仓储/DB模型中的result_count字段
- 清理worker中对plan.result_count的写入
- 创建048 migration删除edit_plans.result_count列
- 该字段为剪辑计划独立功能遗留，生成结果数由generation_tasks承载
- net: -6行 + 1 migration

packages/adapters/sqlalchemy_impl/edit_plan_repository.py

@@ -100,7 +100,6 @@ class SQLAlchemyEditPlanRepository:
             name=plan.name,
             status=plan.status,
             total_duration=plan.total_duration,
-            result_count=plan.result_count,
             source_edit_plan_id=plan.source_edit_plan_id or None,
             project_id=plan.project_id or "",
             created_by_user_id=plan.created_by_user_id or "",
@@ -120,7 +119,6 @@ class SQLAlchemyEditPlanRepository:
         model.name = plan.name
         model.status = plan.status
         model.total_duration = plan.total_duration
-        model.result_count = plan.result_count
         model.source_edit_plan_id = plan.source_edit_plan_id or None
         model.project_id = plan.project_id or ""
         model.created_by_user_id = plan.created_by_user_id or ""
@@ -154,7 +152,6 @@ class SQLAlchemyEditPlanRepository:
             name=model.name,
             status=EditPlanStatus(model.status) if model.status else EditPlanStatus.DRAFT,
             total_duration=model.total_duration or 0.0,
-            result_count=int(model.result_count or 0),
             source_edit_plan_id=model.source_edit_plan_id or "",
             project_id=model.project_id or "",
             created_by_user_id=model.created_by_user_id or "",

packages/adapters/sqlalchemy_impl/models.py

@@ -172,7 +172,6 @@ class EditPlanModel(Base):
     name = Column(String(200), nullable=False)
     status = Column(String(20), nullable=False, default="draft", index=True)
     total_duration = Column(Float, nullable=False, default=0.0)
-    result_count = Column(Integer, nullable=False, default=0)
     config = Column(JSON, nullable=False, default=dict)
     source_edit_plan_id = Column(String(36), nullable=True, index=True)
     project_id = Column(String(36), nullable=False, default="", index=True)