💥 feat(agent)!: 添加主机监控代理首版

* 实现周期采集、快照缓存、本地 HTTP API 和主动上报

* 补齐 Linux 和 Windows 主机、网络、资源、进程和 TCP 采集

* 添加服务生命周期管理、配置加载、构建脚本和测试覆盖

BREAKING CHANGE: network.ips 拆分为 network.ipv4s 和 network.ipv6s。

README.md

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+# MFD Monitor Agent
+
+Single-binary host status agent implemented in Go.
+
+## Features
+
+- `GET /health` returns process liveness and latest snapshot metadata.
+- `GET /status` returns the cached full host snapshot.
+- Periodic background collection keeps HTTP responses fast.
+- Optional periodic HTTP POST reporting reuses the same `HostStatus` JSON.
+- Linux collectors read host, network, CPU, memory, disk, process, and TCP listener data from the OS.
+- Windows and Linux service lifecycle commands are exposed through the CLI.
+
+## Commands
+
+```bash
+agent run [-config config.json]
+agent install [-config config.json] [-exe /path/to/agent]
+agent uninstall [-config config.json]
+agent start [-config config.json]
+agent stop [-config config.json]
+agent version
+```
+
+## Build
+
+Linux:
+
+```bash
+./scripts/build-linux.sh
+```
+
+Windows PowerShell:
+
+```powershell
+.\scripts\build-windows.ps1
+```
+
+Cross-compile Windows from Linux:
+
+```bash
+GOOS_TARGET=windows GOARCH_TARGET=amd64 OUTPUT_NAME=agent-windows-amd64.exe ./scripts/build-linux.sh
+```
+
+Build outputs are written to `dist/`, which is intentionally ignored by Git.
+
+## Configuration
+
+All settings have safe defaults. The HTTP API listens on `127.0.0.1:8080` by default.
+
+```json
+{
+  "host_id": "host-a",
+  "http": {
+    "listen_address": "127.0.0.1:8080"
+  },
+  "collect": {
+    "interval": "30s",
+    "timeout": "10s"
+  },
+  "report": {
+    "enabled": true,
+    "endpoint": "http://center.example.internal/agent/status",
+    "interval": "60s",
+    "timeout": "5s"
+  }
+}
+```
+
+Environment overrides:
+
+- `MFD_AGENT_HOST_ID`
+- `MFD_AGENT_LISTEN`
+- `MFD_AGENT_COLLECT_INTERVAL`
+- `MFD_AGENT_COLLECT_TIMEOUT`
+- `MFD_AGENT_REPORT_ENABLED`
+- `MFD_AGENT_REPORT_ENDPOINT`
+- `MFD_AGENT_REPORT_INTERVAL`
+- `MFD_AGENT_REPORT_TIMEOUT`