Covers the landed-worktree sweep: which signals count as landed, every keep-the-checkout guard (live runs, gone branches, unreadable state, rejected or failed runs), and — against real git — that a removed checkout's branch, commits, and uncommitted leftovers survive.

## Before writing SPEC.md files

Read https://raw.githubusercontent.com/brillout/sdd/refs/heads/main/sdd.md
