feat(api): 收敛对话与记忆流程边界，引入 LLM 网关与专用服务

- MemoryService 异步路径委托 MemoryIngestService / MemoryRetrievalService；富化派发经 MemoryEnrichmentScheduler
- WebSocket pipeline 经 ChatTurnService 与显式 DTO 编排单轮对话；回忆录片段入队由 MemoirIngestScheduler 封装
- 新增 LlmGateway（LlmUseCase），各 agent、任务与适配器对齐 ports
- 补充 memory 提示适配、runtime 类型、memory-retrieval 文档、ai-touchpoints 说明与扫描脚本及配套测试

Made-with: Cursor

api/app/features/conversation/chat_turn.py

@@ -0,0 +1,116 @@
+"""Conversation chat turn boundary.
+
+This module gives the WebSocket pipeline a small, explicit contract for one
+user turn. It deliberately keeps the existing ``ChatOrchestrator`` behavior
+intact while making the runtime inputs/outputs visible and testable.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from dataclasses import dataclass
+from datetime import datetime
+from typing import Any
+
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.agents.chat import ChatOrchestrator
+from app.agents.chat.agent_turn import AgentChatTurn
+
+
+@dataclass(frozen=True)
+class ChatTurnInput:
+    """Transport-neutral input for a single user chat turn."""
+
+    conversation_id: str
+    user_message: str
+    is_from_voice: bool = False
+    voice_session_id: str | None = None
+    user_message_timestamp: datetime | None = None
+    audio_duration_seconds: int | None = None
+    force_skip_tts: bool = False
+
+
+@dataclass(frozen=True)
+class ChatTurnContext:
+    """Runtime dependencies needed to execute a turn."""
+
+    db: AsyncSession
+    user: Any | None
+    conversation: Any | None
+    apply_extracted_profile_fn: Callable[..., Any]
+    get_missing_profile_fields_fn: Callable[[Any], list[str]]
+    get_filled_profile_fields_fn: Callable[[Any], dict[str, Any]]
+
+
+@dataclass(frozen=True)
+class ChatTurnDecision:
+    """Observable decision metadata for the chat runtime boundary."""
+
+    engine: str = "ChatOrchestrator"
+    route_hint: str = "auto"
+    force_skip_tts: bool = False
+
+
+@dataclass(frozen=True)
+class ChatTurnResult:
+    """Stable result shape consumed by conversation persistence and delivery."""
+
+    messages: list[str]
+    skip_tts: bool
+    memory_retrieval_trace: dict[str, Any] | None = None
+    interview_state_meta: dict[str, Any] | None = None
+    decision: ChatTurnDecision = ChatTurnDecision()
+
+    @classmethod
+    def from_agent_turn(
+        cls,
+        turn: AgentChatTurn,
+        *,
+        decision: ChatTurnDecision,
+    ) -> "ChatTurnResult":
+        return cls(
+            messages=list(turn.messages or []),
+            skip_tts=bool(turn.skip_tts or decision.force_skip_tts),
+            memory_retrieval_trace=turn.memory_retrieval_trace,
+            interview_state_meta=turn.interview_state_meta,
+            decision=decision,
+        )
+
+
+class ChatTurnService:
+    """Executes one chat turn behind an explicit internal contract."""
+
+    def __init__(self, orchestrator: ChatOrchestrator | None = None) -> None:
+        self._orchestrator = orchestrator or ChatOrchestrator()
+
+    async def process_turn(
+        self,
+        turn_input: ChatTurnInput,
+        context: ChatTurnContext,
+    ) -> ChatTurnResult:
+        decision = ChatTurnDecision(force_skip_tts=turn_input.force_skip_tts)
+        turn = await self._orchestrator.process_user_message(
+            conversation_id=turn_input.conversation_id,
+            user_message=turn_input.user_message,
+            user=context.user,
+            conversation=context.conversation,
+            is_from_voice=turn_input.is_from_voice,
+            voice_session_id=turn_input.voice_session_id,
+            db=context.db,
+            apply_extracted_profile_fn=context.apply_extracted_profile_fn,
+            get_missing_profile_fields_fn=context.get_missing_profile_fields_fn,
+            get_filled_profile_fields_fn=context.get_filled_profile_fields_fn,
+            user_message_timestamp=turn_input.user_message_timestamp,
+            audio_duration_seconds=turn_input.audio_duration_seconds,
+        )
+        return ChatTurnResult.from_agent_turn(turn, decision=decision)
+
+
+__all__ = [
+    "ChatTurnContext",
+    "ChatTurnDecision",
+    "ChatTurnInput",
+    "ChatTurnResult",
+    "ChatTurnService",
+]