feat(updater): 引入 24 小时静默更新检测与一键升级功能

- 新增 `updater` 模块实现 GitHub Release 版本异步检查与本地缓存
- 新增 `git air update` 与 `git air version` 命令支持一键升级及版本检查
- 优化 CLI 终端交互，在首页渲染时提供友好的新版本升级提示卡片

internal/updater/checker_test.go

@@ -0,0 +1,30 @@
+package updater
+
+import (
+	"testing"
+)
+
+func TestIsNewerVersion(t *testing.T) {
+	tests := []struct {
+		latest   string
+		current  string
+		expected bool
+	}{
+		{"v1.0.5", "v1.0.4", true},
+		{"v1.1.0", "v1.0.4", true},
+		{"v2.0.0", "v1.9.9", true},
+		{"v1.0.4", "v1.0.4", false},
+		{"v1.0.3", "v1.0.4", false},
+		{"v1.0.4.1", "v1.0.4", true},
+		{"1.0.5", "1.0.4", true},
+		{"", "v1.0.4", false},
+		{"v1.0.4", "", false},
+	}
+
+	for _, tt := range tests {
+		got := IsNewerVersion(tt.latest, tt.current)
+		if got != tt.expected {
+			t.Errorf("IsNewerVersion(%q, %q) = %v, expected %v", tt.latest, tt.current, got, tt.expected)
+		}
+	}
+}