"""Loop core: the single state-transition authority and the shadow watcher.

Issue #5 phase 2a. Two things live here and they are deliberately separated:

  * `lib_py.delegation.engine` decides and commits state. It is the only writer
    of job status, and it lives with the other registry writers rather than here
    -- see that module's docstring for why the package boundary matters under a
    frozen loop.
  * `watcher` observes and never decides; `policy` decides and never writes;
    `shadow` runs the two together and only logs what it *would* have committed.
  * `autocomplete` is the phase 2b gate: it supplies verified evidence to that
    same decision and, only if every gate holds, asks the transition boundary to
    commit. It is off by default and has no production caller yet.

Package rule, enforced by test: nothing here imports a `lib_py` module other
than `lib_py.delegation`. Under a frozen loop the parent package may resolve to
a different tree than a bound sibling, so a stray import silently mixes trees.
"""