Materialize instances when a quest definition is created

create_quest_definition persisted the rule, definition, assignees and
windows but never called regenerate_for_definition, unlike edit, assign,
unassign and activate. A new task therefore had no quest_instances rows
and stayed off the panel board until an unrelated write regenerated it.

Call regenerate_for_definition after the DAO write, using the host
clock and the default horizon, and add a test that a created weekly
definition has only today-or-later instances.

Update test fixtures that relied on create writing no instances: close
the seeded one-day rules with end_date, clear the table before the gated
materialize walk, and adjust the admin regenerate tests to the new
create behaviour.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_materialize.py

@@ -468,7 +468,11 @@ async def _materialize_with_change(
     proceeds with the snapped presence).  This deterministically
     exercises the snapshot-to-insert gap that a config edit can
     interleave into.
+
+    ``create_quest_definition`` already materializes its horizon, so the
+    table is cleared first: the gated walk must be the only writer.
     """
+    await database.execute("DELETE FROM quest_instances")
     original_upsert = QuestInstancesDao.upsert_if_valid
     entered = asyncio.Event()
     release = asyncio.Event()