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/SimulationClock.gd

@@ -4,6 +4,7 @@ extends RefCounted
 var tick_interval: float
 var accumulator := 0.0
 var elapsed_ticks := 0
+var cycle_duration_seconds := 240.0
 
 
 func _init(interval: float = 1.0) -> void:
@@ -23,3 +24,8 @@ func advance(delta: float) -> int:
 func reset() -> void:
 	accumulator = 0.0
 	elapsed_ticks = 0
+
+
+func time_of_day() -> float:
+	var total_seconds := elapsed_ticks * tick_interval + accumulator
+	return fmod(total_seconds / maxf(cycle_duration_seconds, 1.0), 1.0)