refactor(api): W7 tools 注册表拆分（RAG / Text2SQL 子模块）

api/tool_models.py

@@ -0,0 +1,42 @@
+from __future__ import annotations
+
+from collections.abc import Awaitable, Callable
+from dataclasses import dataclass
+from typing import Any, Literal
+
+
+@dataclass(frozen=True)
+class ToolResult:
+    """Tool 执行结果（Agent 仅依赖 error_code/error_stage 做失败类型判定）。"""
+
+    success: bool
+    data: dict[str, Any] | None = None
+    error: str | None = None
+    error_code: str | None = None
+    error_stage: str | None = None
+    latency_ms: int = 0
+
+
+ToolName = Literal["rag_search", "text2sql_query", "direct_answer"]
+
+
+@dataclass(frozen=True)
+class Tool:
+    name: ToolName
+    description: str
+    parameters: dict[str, Any]
+    execute: Callable[..., Awaitable[ToolResult]]
+
+
+class ToolRegistry:
+    def __init__(self) -> None:
+        self._tools: dict[str, Tool] = {}
+
+    def register(self, tool: Tool) -> None:
+        self._tools[tool.name] = tool
+
+    def get(self, name: str) -> Tool | None:
+        return self._tools.get(name)
+
+    def list_tools(self) -> list[Tool]:
+        return list(self._tools.values())