feat: allow local repo reference clones to save disk

Use git --reference-if-able when a local repo is provided so rigs and crew share objects without changing remotes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/rig.go

@@ -251,6 +251,7 @@ Examples:
 // Flags
 var (
 	rigAddPrefix       string
+	rigAddLocalRepo    string
 	rigResetHandoff    bool
 	rigResetMail       bool
 	rigResetStale      bool
@@ -279,6 +280,7 @@ func init() {
 	rigCmd.AddCommand(rigStopCmd)
 
 	rigAddCmd.Flags().StringVar(&rigAddPrefix, "prefix", "", "Beads issue prefix (default: derived from name)")
+	rigAddCmd.Flags().StringVar(&rigAddLocalRepo, "local-repo", "", "Local repo path to share git objects (optional)")
 
 	rigResetCmd.Flags().BoolVar(&rigResetHandoff, "handoff", false, "Clear handoff content")
 	rigResetCmd.Flags().BoolVar(&rigResetMail, "mail", false, "Clear stale mail messages")
@@ -330,6 +332,9 @@ func runRigAdd(cmd *cobra.Command, args []string) error {
 
 	fmt.Printf("Creating rig %s...\n", style.Bold.Render(name))
 	fmt.Printf("  Repository: %s\n", gitURL)
+	if rigAddLocalRepo != "" {
+		fmt.Printf("  Local repo: %s\n", rigAddLocalRepo)
+	}
 
 	startTime := time.Now()
 
@@ -338,6 +343,7 @@ func runRigAdd(cmd *cobra.Command, args []string) error {
 		Name:        name,
 		GitURL:      gitURL,
 		BeadsPrefix: rigAddPrefix,
+		LocalRepo:   rigAddLocalRepo,
 	})
 	if err != nil {
 		return fmt.Errorf("adding rig: %w", err)