feat(bead): add 'gt bead show' subcommand

Adds show subcommand to gt bead that delegates to gt show (which
delegates to bd show). This completes gt-zdwy58.

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

internal/cmd/bead.go

@@ -39,9 +39,28 @@ Examples:
 
 var beadMoveDryRun bool
 
+var beadShowCmd = &cobra.Command{
+	Use:   "show <bead-id> [flags]",
+	Short: "Show details of a bead",
+	Long: `Displays the full details of a bead by ID.
+
+This is an alias for 'gt show'. All bd show flags are supported.
+
+Examples:
+  gt bead show gt-abc123          # Show a gastown issue
+  gt bead show hq-xyz789          # Show a town-level bead
+  gt bead show bd-def456          # Show a beads issue
+  gt bead show gt-abc123 --json   # Output as JSON`,
+	DisableFlagParsing: true, // Pass all flags through to bd show
+	RunE: func(cmd *cobra.Command, args []string) error {
+		return runShow(cmd, args)
+	},
+}
+
 func init() {
 	beadMoveCmd.Flags().BoolVarP(&beadMoveDryRun, "dry-run", "n", false, "Show what would be done")
 	beadCmd.AddCommand(beadMoveCmd)
+	beadCmd.AddCommand(beadShowCmd)
 	rootCmd.AddCommand(beadCmd)
 }