cli: do not use interactive TUI elements when control terminal (tty) is not available (fixes #386)

internal/cli/tui/spinner.go

@@ -0,0 +1,37 @@
+package tui
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"charm.land/huh/v2/spinner"
+	"charm.land/lipgloss/v2"
+)
+
+// RunSpinner shows an animated spinner that prints title while running action.
+// When the terminal (TTY) is not available, it prints the title as plain text.
+// It renders to stderr so stdout stays clean for command output.
+func RunSpinner(ctx context.Context, title string, action func(ctx context.Context) error) error {
+	// Fall back to plain text when a terminal is not available to avoid the bubbletea /dev/tty error and to keep
+	// escape codes out of redirected output.
+	if !IsTerminalAvailable() {
+		fmt.Fprintln(os.Stderr, title)
+		return action(ctx)
+	}
+
+	return spinner.New().
+		// Leading space offsets the title from the spinner glyph.
+		Title(" " + title).
+		Type(spinner.MiniDot).
+		WithTheme(spinner.ThemeFunc(func(isDark bool) *spinner.Styles {
+			return &spinner.Styles{
+				Spinner: lipgloss.NewStyle().Foreground(lipgloss.Yellow),
+				Title:   lipgloss.NewStyle(),
+			}
+		})).
+		WithOutput(os.Stderr).
+		Context(ctx).
+		ActionWithErr(action).
+		Run()
+}