new shape: applied is git-init'd at first spawn, fetches
proposed's initial commit into its main, tags deployed/0 there.
the wrapper flake.nix is regenerated on every spawn/rebuild
but no longer tracked — apply churn vanishes, manager-authored
files in the proposal flow now survive untouched. setup_applied
gains an Option<&Path> for proposed (None on rebuild paths
that just refresh the flake). pre-overhaul applied dirs are
detected via the missing deployed/0 tag and bail loudly with
the destroy --purge migration hint. apply_commit is stubbed
with a clear error until the tag-driven approve flow lands.
8cb8fcedad