feat: add NPC schedules with sleep, meal, and work periods

Add ACTION_SLEEP with home-position targeting and energy restoration. Embed schedule periods (SLEEP/MEAL/WORK/DISCRETIONARY) in ActionSelectionSystem with TimeOfDay from SimulationClock. NPCs sleep at night when energy is low, eat during meal periods when hungry, and work/discretionary the rest of the cycle. Home position stored per NPC and serialized through NPCStateRecord with backward-compatible fallback. Cycle duration persisted through save/restore. Includes headless test for sleep period, work period, meal hunger, energy restoration, serialization round-trip, and home targeting without world adapter.

simulation/definitions/actions/sleep.tres

@@ -0,0 +1,10 @@
+[gd_resource type="Resource" script_class="ActionDefinition" load_steps=2 format=3]
+
+[ext_resource type="Script" path="res://simulation/definitions/ActionDefinition.gd" id="1"]
+
+[resource]
+script = ExtResource("1")
+action_id = &"sleep"
+display_name = "Sleep"
+default_duration = 8.0
+target_type = &"free"