063-land-verbs

The land verbs wait for, arm, push and restack a pull request, and land status orders what is left

Amends spec 006's command surface; its four write verbs act under the F-02 narrowing of 2026-10-27 and never inside a run attempt (D-5). Six verbs act on a pull request's way to the default branch through the operator's gh: `land wait` blocks until a named event, `land arm` enables auto-merge only for a head the AI review passed on a pull request based on the default branch, `land push` pushes a signed head with a lease after disarming, `land restack` moves a stacked pull request onto its new base and regenerates only declared generated paths, and `land status` orders the open pull requests by their next action, and `land cancel-superseded` cancels runs no open pull request needs. The adopter's values (default branch, stack caps, generated paths and their regenerators, pre-push checks) come from a `landing` block in the project declaration; a value no layer supplies is refused, never defaulted. Only `land arm` arms, and nothing here approves, merges or re-runs.