South town MVP: world sim, seasons, granary, contrast test + findings

Godot 4.7 C# world simulation per SPEC.md (with 2026-07-21 amendments).
15 NPCs, 5-state machine, demand-driven work, soul-imprint triad data
model, seasons with winter frost, granary, need-based gift economy,
selfish-soul contrast wiring, daily/per-villager/gift CSV logging.

FINDINGS.md documents the four soak experiments: the dead paradise,
the buffers winning, the emergent hungry gap, and the contrast test
proving the four-town thesis (and that selfishness wins until the
soul-consequence layer exists).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/SaveSystem.cs

@@ -0,0 +1,34 @@
+using Godot;
+
+namespace WorldSim;
+
+/// <summary>
+/// World-state serialization (SPEC §9 amendment).
+/// "The world is the save file" — persistence is a first-class MVP system,
+/// not a Phase 4 afterthought. Baseline test: save → load → the simulation
+/// continues identically (round-trip).
+///
+/// TODO(Week 4): serialize World.Nodes, Npcs (position, state, inventory,
+/// fatigue, health, imprint triad), Buildings, and TotalTicks to JSON at
+/// user://worldsim_save.json; load must rebuild identical state.
+/// Design note carried from DESIGN.md: when object imprint histories arrive
+/// (Phase 3), old imprints compress into net values + a few significant
+/// preserved entries — "what the world remembers in detail vs. aggregate"
+/// is a design decision expressed as a data policy.
+/// </summary>
+public static class SaveSystem
+{
+    public static string SavePath => "user://worldsim_save.json";
+
+    public static void Save(GameManager gm)
+    {
+        // TODO(Week 4): implement JSON round-trip.
+        GD.Print("[SaveSystem] Save not yet implemented.");
+    }
+
+    public static bool TryLoad(GameManager gm)
+    {
+        // TODO(Week 4): implement JSON round-trip.
+        return false;
+    }
+}