fix: 完善苹果系统构建与文件兼容

动机：解决苹果系统发布包缺少执行权限和特殊文件误处理问题。
改动：校验发布包权限，支持两类芯片架构并改进文件识别。
影响：苹果系统可直接运行发布包，其他平台构建与使用方式兼容。
验证：运行 go test ./...、go vet ./... 和完整发布构建，结果通过。
关联：无

main_test.go

@@ -0,0 +1,27 @@
+package main
+
+import "testing"
+
+func TestIsNCMFile(t *testing.T) {
+	tests := []struct {
+		name string
+		path string
+		want bool
+	}{
+		{name: "lowercase", path: "/Users/test/Music/song.ncm", want: true},
+		{name: "uppercase", path: "/Users/test/Music/song.NCM", want: true},
+		{name: "unicode path", path: "/Users/test/音乐/歌曲.ncm", want: true},
+		{name: "macOS AppleDouble file", path: "/Users/test/Music/._song.ncm", want: false},
+		{name: "short name", path: "a", want: false},
+		{name: "extension only", path: ".ncm", want: true},
+		{name: "different extension", path: "song.flac", want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := isNCMFile(tt.path); got != tt.want {
+				t.Fatalf("isNCMFile(%q) = %v, want %v", tt.path, got, tt.want)
+			}
+		})
+	}
+}