feat(cli): add --quiet flag and ProgressFromCmd helper

Wire the Progress interface into the CLI by adding a --quiet/-q global
flag and a ProgressFromCmd helper that returns QuietProgress (stderr)
when --quiet is set, or DefaultProgress (TTY-aware) otherwise.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cmd/context.go

@@ -0,0 +1,17 @@
+package cmd
+
+import (
+	"os"
+
+	"github.com/Snider/Borg/pkg/ui"
+	"github.com/spf13/cobra"
+)
+
+// ProgressFromCmd returns a Progress based on --quiet flag and TTY detection.
+func ProgressFromCmd(cmd *cobra.Command) ui.Progress {
+	quiet, _ := cmd.Flags().GetBool("quiet")
+	if quiet {
+		return ui.NewQuietProgress(os.Stderr)
+	}
+	return ui.DefaultProgress()
+}

cmd/context_test.go

@@ -0,0 +1,28 @@
+package cmd
+
+import (
+	"testing"
+
+	"github.com/spf13/cobra"
+)
+
+func TestProgressFromCmd_Good(t *testing.T) {
+	cmd := &cobra.Command{}
+	cmd.PersistentFlags().BoolP("quiet", "q", false, "")
+
+	p := ProgressFromCmd(cmd)
+	if p == nil {
+		t.Fatal("expected non-nil Progress")
+	}
+}
+
+func TestProgressFromCmd_Quiet_Good(t *testing.T) {
+	cmd := &cobra.Command{}
+	cmd.PersistentFlags().BoolP("quiet", "q", true, "")
+	_ = cmd.PersistentFlags().Set("quiet", "true")
+
+	p := ProgressFromCmd(cmd)
+	if p == nil {
+		t.Fatal("expected non-nil Progress")
+	}
+}

cmd/root.go

@@ -16,6 +16,7 @@ packaging their contents into a single file, and managing the data within.`,
 	}
 
 	rootCmd.PersistentFlags().BoolP("verbose", "v", false, "Enable verbose logging")
+	rootCmd.PersistentFlags().BoolP("quiet", "q", false, "Suppress non-error output")
 	return rootCmd
 }