Add directory recursion for Add and mirror up/down commands.

Add now recursively walks directories instead of creating a single
"directory" type entry. Extract addEntry helper for reuse. Implement
MirrorUp (sync filesystem state into manifest) and MirrorDown (sync
manifest state to filesystem with untracked file cleanup). Add CLI
mirror command with up/down subcommands.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/sgard/mirror.go

@@ -0,0 +1,72 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/kisom/sgard/garden"
+	"github.com/spf13/cobra"
+)
+
+var forceMirror bool
+
+var mirrorCmd = &cobra.Command{
+	Use:   "mirror",
+	Short: "Sync directory contents between filesystem and manifest",
+}
+
+var mirrorUpCmd = &cobra.Command{
+	Use:   "up <path>...",
+	Short: "Sync filesystem state into manifest (add new, remove deleted, rehash changed)",
+	Args:  cobra.MinimumNArgs(1),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		g, err := garden.Open(repoFlag)
+		if err != nil {
+			return err
+		}
+
+		if err := g.MirrorUp(args); err != nil {
+			return err
+		}
+
+		fmt.Println("Mirror up complete.")
+		return nil
+	},
+}
+
+var mirrorDownCmd = &cobra.Command{
+	Use:   "down <path>...",
+	Short: "Sync manifest state to filesystem (restore tracked, delete untracked)",
+	Args:  cobra.MinimumNArgs(1),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		g, err := garden.Open(repoFlag)
+		if err != nil {
+			return err
+		}
+
+		confirm := func(path string) bool {
+			fmt.Printf("Delete untracked file %s? [y/N] ", path)
+			scanner := bufio.NewScanner(os.Stdin)
+			if scanner.Scan() {
+				answer := strings.TrimSpace(strings.ToLower(scanner.Text()))
+				return answer == "y" || answer == "yes"
+			}
+			return false
+		}
+
+		if err := g.MirrorDown(args, forceMirror, confirm); err != nil {
+			return err
+		}
+
+		fmt.Println("Mirror down complete.")
+		return nil
+	},
+}
+
+func init() {
+	mirrorDownCmd.Flags().BoolVarP(&forceMirror, "force", "f", false, "delete untracked files without prompting")
+	mirrorCmd.AddCommand(mirrorUpCmd, mirrorDownCmd)
+	rootCmd.AddCommand(mirrorCmd)
+}