Step 7: Add remove command to stop tracking files.

Implements Garden.Remove() which unregisters paths from the manifest,
plus unit tests and the CLI wiring via cobra.

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

cmd/sgard/remove.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/kisom/sgard/garden"
+	"github.com/spf13/cobra"
+)
+
+var removeCmd = &cobra.Command{
+	Use:   "remove <path>...",
+	Short: "Stop tracking files",
+	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.Remove(args); err != nil {
+			return err
+		}
+
+		fmt.Printf("Removed %d path(s)\n", len(args))
+		return nil
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(removeCmd)
+}