feat(pulls): support branch-validated stack reordering

Assisted-by: Codet:GPT-5-Codex

cmd/pulls/stack.go

@@ -15,13 +15,14 @@ import (
 var CmdPullsStack = cli.Command{
 	Name:        "stack",
 	Usage:       "Manage pull request stacks",
-	Description: "List, show, push, restack, and merge pull request stacks",
+	Description: "List, show, push, reorder, restack, and merge pull request stacks",
 	Action:      runPullsStackDefault,
 	Commands: []*cli.Command{
 		&stack.CmdStackList,
 		&stack.CmdStackShow,
 		&stack.CmdStackPush,
 		&stack.CmdStackRestack,
+		&stack.CmdStackReorder,
 		&stack.CmdStackMerge,
 	},
 }