PresenceEngine gains an overrides snapshot (child_id -> list of
PresenceOverride): is_present checks covering overrides BEFORE the
pattern and returns the override's flag as the answer — an absent
override on a normally-present day returns False, a present one on a
normally-absent day returns True, and an override on a child with no
schedule still applies (holidays work for the always-present sibling).
Snapshot validation mirrors the schedules': dict of lists keyed by the
override's own child id, exposed read-only. The DAO layer guarantees
no overlapping overrides per child; a hand-built snapshot that carries
them resolves deterministically to the LATEST start date (documented).
Tests: all three precedence cases, span edges (outside days stay on
the pattern), snapshot rejection matrix, deterministic overlap
tie-break. Suite: 995 passed.
Joshua King
8f04d93363