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/ui/render.go

@@ -52,6 +52,19 @@ func PrintUsage(inputTokens, outputTokens int, costUSD float64) {
 	)
 }
 
+// PrintUpdateBanner 打印新版本升级提醒卡片
+func PrintUpdateBanner(currentVer, latestVer, releaseURL string) {
+	fmt.Println()
+	fmt.Println(colorYellow + "┌─────────────────────────────────────────────────────────────┐" + colorReset)
+	fmt.Printf(colorYellow+"│"+colorReset+"  🚀 %sgit-air 新版本发布: %s%s%s → %s%s%s\n",
+		colorBold, colorGray, currentVer, colorReset,
+		colorGreen, latestVer, colorReset,
+	)
+	fmt.Println(colorYellow + "│" + colorReset + "  运行以下命令一键升级:                                      " + colorYellow + "│" + colorReset)
+	fmt.Printf(colorYellow+"│"+colorReset+"  %sgo install github.com/unclesam-ly/git-air@latest%s          "+colorYellow+"│"+colorReset+"\n", colorCyan, colorReset)
+	fmt.Println(colorYellow + "└─────────────────────────────────────────────────────────────┘" + colorReset)
+}
+
 // PrintError 打印错误信息
 func PrintError(format string, a ...interface{}) {
 	msg := fmt.Sprintf(format, a...)

internal/updater/checker.go

@@ -0,0 +1,173 @@
+package updater
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// CurrentVersion 当前编译版本号
+const CurrentVersion = "v1.0.4"
+
+const (
+	githubAPIURL  = "https://api.github.com/repos/unclesam-ly/git-air/releases/latest"
+	checkInterval = 24 * time.Hour
+	httpTimeout   = 1500 * time.Millisecond
+)
+
+type UpdateState struct {
+	LastChecked int64  `json:"last_checked"`
+	LatestVer   string `json:"latest_ver"`
+	ReleaseURL  string `json:"release_url"`
+}
+
+type UpdateInfo struct {
+	CurrentVersion string
+	LatestVersion  string
+	ReleaseURL     string
+}
+
+func getCachePath() (string, error) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", err
+	}
+	dir := filepath.Join(home, ".git-air")
+	_ = os.MkdirAll(dir, 0755)
+	return filepath.Join(dir, "update_check.json"), nil
+}
+
+func readCache() (*UpdateState, error) {
+	path, err := getCachePath()
+	if err != nil {
+		return nil, err
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	var state UpdateState
+	if err := json.Unmarshal(data, &state); err != nil {
+		return nil, err
+	}
+	return &state, nil
+}
+
+func writeCache(state *UpdateState) {
+	path, err := getCachePath()
+	if err != nil {
+		return
+	}
+	data, err := json.Marshal(state)
+	if err == nil {
+		_ = os.WriteFile(path, data, 0600)
+	}
+}
+
+// CheckUpdate 检查是否有新版本（带 24 小时本地缓存与极短超时，静默处理所有异常）
+func CheckUpdate(force bool) *UpdateInfo {
+	now := time.Now().Unix()
+
+	// 1. 如果不是强制检查，优先读取 24 小时内的本地缓存
+	if !force {
+		if state, err := readCache(); err == nil && state != nil {
+			if now-state.LastChecked < int64(checkInterval.Seconds()) {
+				if IsNewerVersion(state.LatestVer, CurrentVersion) {
+					return &UpdateInfo{
+						CurrentVersion: CurrentVersion,
+						LatestVersion:  state.LatestVer,
+						ReleaseURL:     state.ReleaseURL,
+					}
+				}
+				return nil
+			}
+		}
+	}
+
+	// 2. 发起轻量级 GitHub API 请求
+	ctx, cancel := context.WithTimeout(context.Background(), httpTimeout)
+	defer cancel()
+
+	req, err := http.NewRequestWithContext(ctx, "GET", githubAPIURL, nil)
+	if err != nil {
+		return nil
+	}
+	req.Header.Set("User-Agent", "git-air-cli")
+	req.Header.Set("Accept", "application/vnd.github.v3+json")
+
+	client := &http.Client{Timeout: httpTimeout}
+	resp, err := client.Do(req)
+	if err != nil || resp == nil || resp.StatusCode != http.StatusOK {
+		return nil
+	}
+	defer resp.Body.Close()
+
+	var release struct {
+		TagName string `json:"tag_name"`
+		HTMLURL string `json:"html_url"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&release); err != nil || release.TagName == "" {
+		return nil
+	}
+
+	// 3. 写入本地缓存
+	writeCache(&UpdateState{
+		LastChecked: now,
+		LatestVer:   release.TagName,
+		ReleaseURL:  release.HTMLURL,
+	})
+
+	// 4. 比对版本
+	if IsNewerVersion(release.TagName, CurrentVersion) {
+		return &UpdateInfo{
+			CurrentVersion: CurrentVersion,
+			LatestVersion:  release.TagName,
+			ReleaseURL:     release.HTMLURL,
+		}
+	}
+
+	return nil
+}
+
+// CheckAsync 后台并发静默检查，返回 channel 供主流程结束前快速获取
+func CheckAsync() <-chan *UpdateInfo {
+	ch := make(chan *UpdateInfo, 1)
+	go func() {
+		info := CheckUpdate(false)
+		ch <- info
+	}()
+	return ch
+}
+
+// IsNewerVersion 语义化版本号比对 (如 "v1.0.5" > "v1.0.4")
+func IsNewerVersion(latest, current string) bool {
+	latestClean := strings.TrimPrefix(strings.TrimSpace(latest), "v")
+	currentClean := strings.TrimPrefix(strings.TrimSpace(current), "v")
+
+	if latestClean == "" || currentClean == "" || latestClean == currentClean {
+		return false
+	}
+
+	latestParts := strings.Split(latestClean, ".")
+	currentParts := strings.Split(currentClean, ".")
+
+	for i := 0; i < len(latestParts) && i < len(currentParts); i++ {
+		lNum, err1 := strconv.Atoi(latestParts[i])
+		cNum, err2 := strconv.Atoi(currentParts[i])
+		if err1 != nil || err2 != nil {
+			return latestClean > currentClean
+		}
+		if lNum > cNum {
+			return true
+		} else if lNum < cNum {
+			return false
+		}
+	}
+
+	return len(latestParts) > len(currentParts)
+}

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)
+		}
+	}
+}