feat: add config opt-out, TTY check, and config-first update flow

- Add auto_update_check config field (defaults to true)
- Load config before update check, skip if auto_update_check is false
- Add TTY check before interactive prompt (skip in non-TTY environments)
- Update config.example.yaml with new option documentation

cmd/kctl-tui/main.go

@@ -83,8 +83,18 @@ func main() {
 		}
 	}
 
-	if checkForUpdateInteractive(verbose) {
-		os.Exit(0)
+	// Load config early to check auto_update_update and validate.
+	cfgPath, err := config.DefaultPath()
+	if err == nil {
+		cfg, cfgErr := config.Load(cfgPath)
+		if cfgErr != nil {
+			fmt.Fprintf(os.Stderr, "WARNING: failed to load config: %v\n", cfgErr)
+		}
+		if cfgErr == nil && cfg.IsAutoUpdateCheckEnabled() {
+			if checkForUpdateInteractive(verbose) {
+				os.Exit(0)
+			}
+		}
 	}
 
 	m := newFullModel()

cmd/kctl-tui/update.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/Masterminds/semver/v3"
 	"github.com/creativeprojects/go-selfupdate"
+	"golang.org/x/term"
 )
 
 const (
@@ -88,6 +89,10 @@ func checkForUpdateInteractive(verbose bool) bool {
 		return false
 	}
 
+	if !term.IsTerminal(int(os.Stdin.Fd())) {
+		return false
+	}
+
 	updater, err := initUpdater(verbose)
 	if err != nil {
 		if verbose {