Collapses the two probes #79 and #80 grew in parallel into one: worktree_probe::in_the_way is the single predicate behind the kill refusal, the retained list, and the natural-exit classifier to come. Keeps #79's in-worktree resolution (detached HEAD, missing directory) and #80's InTheWay payload, and drops the duplicate UnsavedWork type. Closes #79