feat: 完成 issue #3 边缘采集网关模板化封装

- 点位字典 CSV schema/加载/自动校验（缺失字段/量纲/重复点号，PRD 5.1）
- 协议可插拔只读驱动：OPC UA(S7-1200 适配)/S7/Modbus/称重/能源/模拟
- 周期采集引擎：只读+背压保护+健康度指标（丢失率/P99/可用性）
- Kafka 流式上行 + 本地 spool 断点续传（丢失率≤0.02% 保障）
- 模板配置外置（gateway.yaml + 点位字典 CSV），换行业零改码
- 18 个单元测试全绿；端到端运行 SLA 达标

core/edge-gateway/drivers/modbus_driver.py

@@ -0,0 +1,79 @@
+# -*- coding: utf-8 -*-
+"""Modbus 驱动 —— PLC / 称重仪表等 RTU/TCP 从站参数化适配。
+
+连接参数（mode / host / port / slave_id / register_map）来自模板配置；
+寄存器映射约定写入点位字典 opcNode 列，格式 `{type}:{addr}`，
+type ∈ holding|input|coil|discrete，如 `holding:40001`。
+依赖 `pymodbus`，未安装时给出明确提示。
+"""
+from __future__ import annotations
+
+from typing import Dict, List, Optional
+
+from point_dict.loader import Point
+from .base import Driver, SampleValue
+
+_REG_MAP = {"holding": 3, "input": 4, "coil": 1, "discrete": 2}
+
+
+class ModbusDriver(Driver):
+    """Modbus 只读采集驱动（参数化适配）。"""
+
+    protocol = "modbus"
+
+    def __init__(self, config: Optional[dict] = None):
+        super().__init__(config)
+        self.mode: str = self.config.get("mode", "tcp")  # tcp | rtu
+        self.host: str = self.config.get("host", "")
+        self.port: int = int(self.config.get("port", 502))
+        self.slave_id: int = int(self.config.get("slave_id", 1))
+        self._client = None
+
+    def connect(self) -> None:
+        try:
+            from pymodbus.client import ModbusTcpClient, ModbusSerialClient  # type: ignore
+        except ImportError as exc:  # pragma: no cover - 依赖缺失路径
+            raise ConnectionError(
+                "Modbus 驱动依赖库未安装：请 `pip install pymodbus`"
+            ) from exc
+        if self.mode == "tcp":
+            if not self.host:
+                raise ConnectionError("Modbus 驱动缺少配置: drivers.modbus.host")
+            self._client = ModbusTcpClient(self.host, port=self.port)
+        else:
+            self._client = ModbusSerialClient(
+                port=self.config.get("port", "COM1"),
+                baudrate=self.config.get("baudrate", 9600),
+            )
+        if not self._client.connect():
+            raise ConnectionError(f"Modbus 连接失败: {self.host or self.config.get('port')}")
+
+    def read_points(self, points: List[Point]) -> Dict[str, SampleValue]:
+        if self._client is None:
+            raise ConnectionError("Modbus 客户端未连接，请先 connect()")
+        result: Dict[str, SampleValue] = {}
+        for p in points:
+            node = (p.opc_node or "").split(":")
+            if len(node) != 2 or node[0] not in _REG_MAP:
+                continue
+            reg_type, addr = node[0], int(node[1])
+            try:
+                if reg_type == "coil":
+                    resp = self._client.read_coils(addr, count=1, slave=self.slave_id)
+                elif reg_type == "discrete":
+                    resp = self._client.read_discrete_inputs(addr, count=1, slave=self.slave_id)
+                else:
+                    resp = self._client.read_holding_registers(addr, count=1, slave=self.slave_id) \
+                        if reg_type == "holding" else \
+                        self._client.read_input_registers(addr, count=1, slave=self.slave_id)
+                result[p.point_id] = resp.registers[0] if hasattr(resp, "registers") and resp.registers else None
+            except Exception:
+                result[p.point_id] = None
+        return result
+
+    def close(self) -> None:
+        if self._client is not None:
+            try:
+                self._client.close()
+            finally:
+                self._client = None