Review round 1 (Codex gpt-5.6-terra, 2 LOW): engine snapshot keys now
pass _validate_child_id (True/1.0 compare equal to 1 and would be
accepted then behave differently on lookup); the always-present test
now walks all 28 days asserting all three children's expected verdicts
instead of sampling every third day. Suite: 985 passed.
PresenceEngine is an immutable, database-free snapshot of the
children's schedules answering is_present(child_id, date): a child
with NO schedule entry is present every day (the household's
always-present sibling); a scheduled child is present exactly when
the date's weekday is in the pattern for that date's cycle week
(anchor-date arithmetic via cycle_week_index — never ISO parity).
Construction validates the snapshot shape (dict keyed by the
schedule's own child_id, values are PresenceSchedules) and exposes it
read-only (MappingProxyType + __setattr__ refusal). is_present
rejects non-int child ids and non-plain dates.
Tests: the three-child fixture (two complementary rotation children,
one schedule-free) asserted for every day of a four-week span plus
spot-checked swap days; weekend/weekday-set behaviour across weeks;
construction/input rejection matrix; engine immutability. Suite:
985 passed.
Joshua King