Address PR #143 review (CHANGES_REQUIRED)

P2.1: Point test_presence.py ISO-week scan at core.presence (the real
model since task 510c1f78); the integration's presence.py is now a
re-export shim, so scanning it was vacuous.

P2.2: Add direct core-builder unit tests to test_events.py — exact
payload key sets for completed/uncompleted/day-complete events,
was_on_time threading (True/False/None), event ordering (completed
fires before day-complete on the bus), and the four day-complete
outcomes (zero-quest day, non-today instance, partial day,
fully-cleared today). Add a shim timezone test that sets
hass.config.time_zone to a zone whose local date differs from UTC and
asserts the day-complete rule uses that local date.

P3.1: Split build_quest_completed_events into
build_quest_completed_event (single event, no day-complete state) and
build_child_day_complete_event (separate, returns the day-complete
event or None). The shim fires nestquest_quest_completed BEFORE it
reads the HA-local today and evaluates the day-complete rule,
restoring the pre-extraction ordering so a failure in the day-complete
DB reads or the ZoneInfo lookup cannot suppress the completed event.
Payloads and the day-complete rule are identical.

P3.2: test_startup_db.py glob -> rglob so core/ is scanned by the
'never unlinks or truncates DB files' guardrail (non-recursive glob
skipped the extracted core package).

P3.3: RELEASE_NOTES.md notes the children and admin_allowlist loggers
moved to .core.children / .core.admin_allowlist (parent logger still
catches them).

P3.4: Refresh the stale test_core_isolation.py docstring to cover the
whole core package (storage-layer task d0b691d8 + engines/business-
layer task 510c1f78).

uv run pytest -q = 1507 passed (baseline 1497 + 10 new).

tests/test_core_isolation.py

@@ -4,9 +4,10 @@ Every module under ``custom_components/nestquest/core/`` must be free of
 Home Assistant and must not climb out of the core package: no
 ``homeassistant`` import, no relative import with level > 1, no absolute
 import of ``custom_components.nestquest.<something other than core>``,
-and no bare ``import core`` / ``from core``.  This guards the
-storage-layer extraction (task d0b691d8) from regressing into a
-HA-coupled or integration-coupled bundle.
+and no bare ``import core`` / ``from core``.  This guards the whole
+core package — the storage-layer extraction (task d0b691d8) and the
+engines/business-layer extraction (task 510c1f78) — from regressing
+into a HA-coupled or integration-coupled bundle.
 """
 from __future__ import annotations