feat(候选端口): 声明批量 Paragraph 工作区能力

在 CandidateWorkspaceRepository 端口增加 create_paragraphs，接收有序段落映射并返回 client_key 到物理 ID 的映射，为事务批量写入提供稳定领域接口。

script_build_host/src/script_build_host/domain/phase_two_ports.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from collections.abc import Mapping, Sequence
 from dataclasses import dataclass
 from typing import Any, Protocol
 
@@ -52,6 +53,10 @@ class CandidateWorkspaceRepository(Protocol):
 
     async def snapshot(self, context: CandidateWriteContext) -> CandidateWorkspaceSnapshot: ...
 
+    async def create_paragraphs(
+        self, context: CandidateWriteContext, paragraphs: Sequence[Mapping[str, Any]]
+    ) -> Mapping[str, int]: ...
+
     async def freeze(
         self,
         context: CandidateWriteContext,