chore: 提交高层 xiaomi 封装库及示例

- 新增 xiaomi/examples/ 下 8 个示例程序（用户/家庭查询、设备列表、开关/灯光/空调控制、属性订阅、高级过滤分类、SPEC 解析）
- miot_client_sub.go: 重构 SubProp/SubEvent，使用 buildPropTopic/buildEventTopic 支持通配符订阅（siid/piid=0 → +），并修复锁顺序问题（将 RequestRefreshProp 移到 Lock 外）
- spec_parser.go: 新增 downloadSpecFile 方法，本地 SPEC 文件缺失时自动从 miot-spec.org 下载
- ARCH_PLAN.md: 架构设计从 Proposed 更新为 Accepted（v1.0→v1.1），补充设备分类/工厂/SPEC 映射等模块设计
- xiaomi/: 新增 miot 上层强类型封装模块，包含 Client 主入口、用户/家庭/设备 API、属性读写、动作调用、订阅通知，以及 devices/ 设备控制抽象（Switch/Light/AirConditioner/Fan/Cover/Humidifier/Vacuum/WaterHeater/Thermostat）和 specs/ SPEC 查询辅助
- 更多 xiaomi 示例（风扇/窗帘/传感器控制）

miot/spec_parser.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"hash/crc32"
+	"io"
 	"log"
 	"math"
 	"net/http"
@@ -216,8 +217,8 @@ func (p *MIoTSpecParser) Parse(urn string, model string) (*MIoTSpecInstance, err
 }
 
 // readSpecFile reads and parses a local JSON spec file from specDir/{urn}.json.
+// If the file doesn't exist, it attempts to download it from miot-spec.org first.
 func (p *MIoTSpecParser) readSpecFile(urn string) (map[string]interface{}, error) {
-	// On Windows, colons are not allowed in filenames
 	fileName := urn
 	if runtime.GOOS == "windows" {
 		fileName = strings.ReplaceAll(urn, ":", "_")
@@ -226,7 +227,16 @@ func (p *MIoTSpecParser) readSpecFile(urn string) (map[string]interface{}, error
 
 	data, err := os.ReadFile(filePath)
 	if err != nil {
-		return nil, fmt.Errorf("read %s: %w", filePath, err)
+		// Auto-download if file not found
+		if os.IsNotExist(err) {
+			if dlErr := p.downloadSpecFile(urn, filePath); dlErr != nil {
+				return nil, fmt.Errorf("download spec: %w", dlErr)
+			}
+			data, err = os.ReadFile(filePath)
+		}
+		if err != nil {
+			return nil, fmt.Errorf("read %s: %w", filePath, err)
+		}
 	}
 
 	var result map[string]interface{}
@@ -236,6 +246,39 @@ func (p *MIoTSpecParser) readSpecFile(urn string) (map[string]interface{}, error
 	return result, nil
 }
 
+// downloadSpecFile downloads a single device spec from miot-spec.org and saves it locally.
+func (p *MIoTSpecParser) downloadSpecFile(urn, filePath string) error {
+	url := fmt.Sprintf("https://miot-spec.org/miot-spec-v2/instance?type=%s", urn)
+
+	httpClient := &http.Client{Timeout: 15 * time.Second}
+	resp, err := httpClient.Get(url)
+	if err != nil {
+		return fmt.Errorf("GET %s: %w", url, err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("GET %s: status %d", url, resp.StatusCode)
+	}
+
+	// Ensure specDir exists
+	if err := os.MkdirAll(filepath.Dir(filePath), 0755); err != nil {
+		return fmt.Errorf("mkdir: %w", err)
+	}
+
+	data, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return fmt.Errorf("read body: %w", err)
+	}
+
+	if err := os.WriteFile(filePath, data, 0644); err != nil {
+		return fmt.Errorf("write %s: %w", filePath, err)
+	}
+
+	log.Printf("[spec] downloaded spec: %s -> %s", urn, filePath)
+	return nil
+}
+
 // parseSpec parses a raw spec dict into a MIoTSpecInstance tree.
 func (p *MIoTSpecParser) parseSpec(urn string, model string, specData map[string]interface{}) (*MIoTSpecInstance, error) {
 	// Get instance description from std lib