Review round 1 (Codex gpt-5.6-terra, 2 MEDIUM): datetime.datetime
subclasses datetime.date and slipped past the anchor check, storing a
time component that would TypeError every later calendar comparison —
rejected explicitly now (both model classes). The frozen schedule's
pattern dict let callers inject unvalidated weekdays or drop required
weeks after construction; the validated mapping is now exposed as a
read-only MappingProxyType over frozenset weeks. Tests: datetime
rejection matrix and immutability assertions. Suite: 974 passed.
Joshua King
cb3c347d61