Persist Ground Zero tile registry baseline

AGRARIAN_DEVELOPMENT_ROADMAP.md

@@ -774,7 +774,10 @@ Target deliverable: A small group can join a server, spawn into one biome, gathe
 - [x] Add load-on-server-start. `AAgrarianGameGameMode` now registers MVP
   persistent actor classes and, when `bLoadWorldOnServerStart` is enabled,
   loads the current world on authoritative `BeginPlay` if a save exists.
-- [ ] Add initial tile registry persistence for Ground Zero.
+- [x] Add initial tile registry persistence for Ground Zero. Saves now include
+  `FAgrarianSavedTileRegistryState` with the active Ground Zero tile ID,
+  registry path, schema version, generation version, and package version while
+  keeping the authoritative registry in `Data/Tiles/ground_zero_tiles.json`.
 - [ ] Add backup-before-save option.
 - [ ] Add recovery plan for corrupted save.
 - [ ] Document persistence limitations.

Docs/PersistenceDesignDocument.md

@@ -437,6 +437,14 @@ inventory persistence. The saved container array is intentionally present now
 so the first placed-container actor can use the same save format without a
 schema break.
 
+Ground Zero tile registry persistence is represented by
+`FAgrarianSavedTileRegistryState` on `UAgrarianSaveGame`. The MVP defaults point
+to active tile `gz_us_ca_pacifica_utm10n_e544_n4160`, registry source
+`Data/Tiles/ground_zero_tiles.json`, registry schema version `1`, generation
+version `1`, and package version `0`. This records the active tile baseline
+inside the save file while the authoritative tile registry remains the external
+JSON registry.
+
 World time is stored in `UAgrarianSaveGame::WorldHours`. The persistence
 subsystem captures it from `AAgrarianGameState::WorldHours` during world save
 and restores it only on authority during world load.

Scripts/verify_ground_zero_tile_registry_persistence.py

@@ -0,0 +1,58 @@
+import json
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+GROUND_ZERO_TILE_ID = "gz_us_ca_pacifica_utm10n_e544_n4160"
+
+EXPECTED = {
+    ROOT / "Source" / "AgrarianGame" / "AgrarianSaveGame.h": [
+        "struct FAgrarianSavedTileRegistryState",
+        f"FName ActiveTileId = TEXT(\"{GROUND_ZERO_TILE_ID}\");",
+        "FString RegistryPath = TEXT(\"Data/Tiles/ground_zero_tiles.json\");",
+        "int32 RegistrySchemaVersion = 1;",
+        "int32 GenerationVersion = 1;",
+        "int32 PackageVersion = 0;",
+        "FAgrarianSavedTileRegistryState TileRegistry;",
+    ],
+    ROOT / "Docs" / "PersistenceDesignDocument.md": [
+        "`FAgrarianSavedTileRegistryState`",
+        f"active tile `{GROUND_ZERO_TILE_ID}`",
+        "`Data/Tiles/ground_zero_tiles.json`",
+    ],
+    ROOT / "AGRARIAN_DEVELOPMENT_ROADMAP.md": [
+        "[x] Add initial tile registry persistence for Ground Zero.",
+        "`FAgrarianSavedTileRegistryState`",
+        "`Data/Tiles/ground_zero_tiles.json`",
+    ],
+}
+
+
+def main() -> None:
+    missing = []
+    registry = json.loads((ROOT / "Data" / "Tiles" / "ground_zero_tiles.json").read_text(encoding="utf-8"))
+    ground_zero = next((tile for tile in registry.get("tiles", []) if tile.get("tile_id") == GROUND_ZERO_TILE_ID), None)
+    if not ground_zero:
+        missing.append("Data/Tiles/ground_zero_tiles.json: Ground Zero tile record")
+    else:
+        if registry.get("schema_version") != 1:
+            missing.append("Data/Tiles/ground_zero_tiles.json: schema_version 1")
+        if ground_zero.get("generation_version") != 1:
+            missing.append("Data/Tiles/ground_zero_tiles.json: generation_version 1")
+        if ground_zero.get("package_version") != 0:
+            missing.append("Data/Tiles/ground_zero_tiles.json: package_version 0")
+
+    for path, snippets in EXPECTED.items():
+        text = path.read_text(encoding="utf-8")
+        for snippet in snippets:
+            if snippet not in text:
+                missing.append(f"{path.relative_to(ROOT)}: {snippet}")
+
+    if missing:
+        raise RuntimeError("Ground Zero tile registry persistence verification failed: " + "; ".join(missing))
+
+    print("PASS: Ground Zero tile registry baseline is represented in save metadata.")
+
+
+if __name__ == "__main__":
+    main()

Source/AgrarianGame/AgrarianSaveGame.h

@@ -106,6 +106,27 @@ struct FAgrarianSavedContainer
 	FString OwnerPlayerId;
 };
 
+USTRUCT(BlueprintType)
+struct FAgrarianSavedTileRegistryState
+{
+	GENERATED_BODY()
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Save")
+	FName ActiveTileId = TEXT("gz_us_ca_pacifica_utm10n_e544_n4160");
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Save")
+	FString RegistryPath = TEXT("Data/Tiles/ground_zero_tiles.json");
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Save")
+	int32 RegistrySchemaVersion = 1;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Save")
+	int32 GenerationVersion = 1;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Save")
+	int32 PackageVersion = 0;
+};
+
 UCLASS()
 class UAgrarianSaveGame : public USaveGame
 {
@@ -138,4 +159,7 @@ public:
 
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Save")
 	TArray<FAgrarianSavedContainer> Containers;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Save")
+	FAgrarianSavedTileRegistryState TileRegistry;
 };