feat: add automatic update notification system

- Implement background version checking with 24-hour caching (follows gh CLI pattern)
- Check GitHub releases API for latest version asynchronously
- Save check state to ~/.openboot/update_state.json
- Show update notification on subsequent runs if newer version available
- Properly handle version comparison with 'v' prefix normalization
- Only check on main installation command to avoid blocking fast commands

Based on research of go-github-selfupdate and gh CLI best practices:
- Non-blocking background checks
- State persistence between runs
- Respects GitHub API rate limits with daily caching
- Clean separation between check and notification phases

Author: fullstackjam

internal/cli/root.go

@@ -6,11 +6,12 @@ import (
 
 	"github.com/openbootdotdev/openboot/internal/config"
 	"github.com/openbootdotdev/openboot/internal/installer"
+	"github.com/openbootdotdev/openboot/internal/updater"
 	"github.com/spf13/cobra"
 )
 
 var (
-	version = "0.14.2"
+	version = "0.14.3"
 	cfg     = &config.Config{}
 )
 
@@ -61,9 +62,12 @@ Self-Update:
 				cfg.Preset = rc.Preset
 			}
 		}
+
 		return nil
 	},
 	RunE: func(cmd *cobra.Command, args []string) error {
+		updater.ShowUpdateNotificationIfAvailable(version)
+		updater.CheckForUpdatesAsync(version)
 		err := installer.Run(cfg)
 		if err == installer.ErrUserCancelled {
 			return nil

internal/installer/installer.go

@@ -31,7 +31,7 @@ func Run(cfg *config.Config) error {
 
 func runInstall(cfg *config.Config) error {
 	fmt.Println()
-	ui.Header("OpenBoot Installer v0.14.2")
+	ui.Header("OpenBoot Installer v0.14.3")
 	fmt.Println()
 
 	if cfg.DryRun {

internal/updater/updater.go

@@ -0,0 +1,130 @@
+package updater
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/openbootdotdev/openboot/internal/ui"
+)
+
+const checkInterval = 24 * time.Hour
+
+type Release struct {
+	TagName string `json:"tag_name"`
+}
+
+type CheckState struct {
+	LastCheck       time.Time `json:"last_check"`
+	LatestVersion   string    `json:"latest_version"`
+	UpdateAvailable bool      `json:"update_available"`
+}
+
+func ShowUpdateNotificationIfAvailable(currentVersion string) {
+	state, err := loadState()
+	if err != nil {
+		return
+	}
+
+	if state.UpdateAvailable && isNewerVersion(state.LatestVersion, currentVersion) {
+		ui.Warn(fmt.Sprintf("New version available: %s (current: v%s)", state.LatestVersion, currentVersion))
+		ui.Muted("Run 'openboot update --self' to upgrade")
+		fmt.Println()
+	}
+}
+
+func CheckForUpdatesAsync(currentVersion string) {
+	go func() {
+		state, _ := loadState()
+
+		if state != nil && time.Since(state.LastCheck) < checkInterval {
+			return
+		}
+
+		latestVersion, err := getLatestVersion()
+		if err != nil {
+			return
+		}
+
+		updateAvailable := isNewerVersion(latestVersion, currentVersion)
+
+		saveState(&CheckState{
+			LastCheck:       time.Now(),
+			LatestVersion:   latestVersion,
+			UpdateAvailable: updateAvailable,
+		})
+	}()
+}
+
+func isNewerVersion(latest, current string) bool {
+	if latest == "" {
+		return false
+	}
+
+	latestClean := trimVersionPrefix(latest)
+	currentClean := trimVersionPrefix(current)
+
+	return latestClean != currentClean && latestClean > currentClean
+}
+
+func trimVersionPrefix(v string) string {
+	if len(v) > 0 && v[0] == 'v' {
+		return v[1:]
+	}
+	return v
+}
+
+func getLatestVersion() (string, error) {
+	client := &http.Client{Timeout: 5 * time.Second}
+	resp, err := client.Get("https://api.github.com/repos/openbootdotdev/openboot/releases/latest")
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("GitHub API returned %d", resp.StatusCode)
+	}
+
+	var release Release
+	if err := json.NewDecoder(resp.Body).Decode(&release); err != nil {
+		return "", err
+	}
+
+	return release.TagName, nil
+}
+
+func getCheckFilePath() string {
+	home, _ := os.UserHomeDir()
+	return filepath.Join(home, ".openboot", "update_state.json")
+}
+
+func loadState() (*CheckState, error) {
+	data, err := os.ReadFile(getCheckFilePath())
+	if err != nil {
+		return nil, err
+	}
+
+	var state CheckState
+	if err := json.Unmarshal(data, &state); err != nil {
+		return nil, err
+	}
+
+	return &state, nil
+}
+
+func saveState(state *CheckState) error {
+	path := getCheckFilePath()
+	dir := filepath.Dir(path)
+	os.MkdirAll(dir, 0755)
+
+	data, err := json.MarshalIndent(state, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	return os.WriteFile(path, data, 0644)
+}