Constant GITHUB_STACKS_KEY 

pub const GITHUB_STACKS_KEY: &str = "stk.githubStacks";

Register a submitted stack with GitHub’s native stacked pull requests. Off by default: the feature is in public preview, so creating a stack on someone’s behalf is opt-in.

Only creating one is gated. Reading a stack, following it, and dissolving it are all unconditional - merge, submit, cleanup, status, repair, and unstack obey a stack GitHub already holds, because a stack made outside git-stk changes what the platform accepts either way: GitHub refuses gh pr merge and gh pr edit --base for a review in one. Undoing a registration must not need the setting that made it, either.