"""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, in this phase, only logs what it *would*
    have committed.

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.
"""