Add server autosave interval

AGRARIAN_DEVELOPMENT_ROADMAP.md

@@ -767,7 +767,9 @@ Target deliverable: A small group can join a server, spawn into one biome, gathe
   item stacks, and owner player ID; 0.1.M has no placed container actor yet, so
   the current craftable `simple_container` remains covered by player inventory
   persistence until placed containers arrive.
-- [ ] Add server-side save interval.
+- [x] Add server-side save interval. `AAgrarianGameGameMode` now starts an
+  authoritative repeating autosave timer from `ServerAutoSaveIntervalSeconds`
+  and calls `SaveCurrentWorld`, with `0` disabling the MVP timer.
 - [x] Add manual admin save command.
 - [ ] Add load-on-server-start.
 - [ ] Add initial tile registry persistence for Ground Zero.

Docs/PersistenceDesignDocument.md

@@ -447,6 +447,12 @@ reapplies the mapped weather inputs; otherwise it restores the saved enum
 weather state. This gives the MVP a deterministic fallback while preserving the
 latest real/provider-mapped tile weather payload when one was available.
 
+The server-side autosave interval lives on `AAgrarianGameGameMode` as
+`ServerAutoSaveIntervalSeconds`, defaulting to five minutes. On authority,
+`BeginPlay` starts a repeating timer that calls `RunServerAutoSave`, which uses
+`UAgrarianPersistenceSubsystem::SaveCurrentWorld`. Setting the interval to zero
+disables the MVP autosave timer.
+
 ## Testing Gates
 
 Minimum persistence smoke test:

Scripts/verify_server_save_interval.py

@@ -0,0 +1,47 @@
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+
+EXPECTED = {
+    ROOT / "Source" / "AgrarianGame" / "AgrarianGameGameMode.h": [
+        "virtual void BeginPlay() override;",
+        "float ServerAutoSaveIntervalSeconds = 300.0f;",
+        "void RunServerAutoSave();",
+        "FTimerHandle ServerAutoSaveTimerHandle;",
+    ],
+    ROOT / "Source" / "AgrarianGame" / "AgrarianGameGameMode.cpp": [
+        "GetWorldTimerManager().SetTimer",
+        "&AAgrarianGameGameMode::RunServerAutoSave",
+        "ServerAutoSaveIntervalSeconds > 0.0f",
+        "Persistence->SaveCurrentWorld()",
+    ],
+    ROOT / "Docs" / "PersistenceDesignDocument.md": [
+        "`ServerAutoSaveIntervalSeconds`",
+        "`UAgrarianPersistenceSubsystem::SaveCurrentWorld`",
+        "disables the MVP autosave timer",
+    ],
+    ROOT / "AGRARIAN_DEVELOPMENT_ROADMAP.md": [
+        "[x] Add server-side save interval.",
+        "`AAgrarianGameGameMode`",
+        "`SaveCurrentWorld`",
+    ],
+}
+
+
+def main() -> None:
+    missing = []
+    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("Server save interval verification failed: " + "; ".join(missing))
+
+    print("PASS: authoritative server autosave interval is wired to world persistence.")
+
+
+if __name__ == "__main__":
+    main()

Source/AgrarianGame/AgrarianGameGameMode.cpp

@@ -5,6 +5,7 @@
 #include "AgrarianDebugHUD.h"
 #include "AgrarianGameState.h"
 #include "AgrarianPersistenceSubsystem.h"
+#include "TimerManager.h"
 
 AAgrarianGameGameMode::AAgrarianGameGameMode()
 {
@@ -12,6 +13,22 @@ AAgrarianGameGameMode::AAgrarianGameGameMode()
 	HUDClass = AAgrarianDebugHUD::StaticClass();
 }
 
+void AAgrarianGameGameMode::BeginPlay()
+{
+	Super::BeginPlay();
+
+	if (HasAuthority() && ServerAutoSaveIntervalSeconds > 0.0f)
+	{
+		GetWorldTimerManager().SetTimer(
+			ServerAutoSaveTimerHandle,
+			this,
+			&AAgrarianGameGameMode::RunServerAutoSave,
+			ServerAutoSaveIntervalSeconds,
+			true,
+			ServerAutoSaveIntervalSeconds);
+	}
+}
+
 void AAgrarianGameGameMode::RestartPlayer(AController* NewPlayer)
 {
 	Super::RestartPlayer(NewPlayer);
@@ -35,3 +52,21 @@ void AAgrarianGameGameMode::Logout(AController* Exiting)
 
 	Super::Logout(Exiting);
 }
+
+void AAgrarianGameGameMode::RunServerAutoSave()
+{
+	if (!HasAuthority())
+	{
+		return;
+	}
+
+	UAgrarianPersistenceSubsystem* Persistence = GetGameInstance() ? GetGameInstance()->GetSubsystem<UAgrarianPersistenceSubsystem>() : nullptr;
+	if (!Persistence)
+	{
+		UE_LOG(LogTemp, Warning, TEXT("Agrarian server autosave skipped: persistence subsystem unavailable."));
+		return;
+	}
+
+	const bool bSaved = Persistence->SaveCurrentWorld();
+	UE_LOG(LogTemp, Log, TEXT("Agrarian server autosave %s."), bSaved ? TEXT("completed") : TEXT("failed"));
+}

Source/AgrarianGame/AgrarianGameGameMode.h

@@ -19,8 +19,17 @@ public:
 	/** Constructor */
 	AAgrarianGameGameMode();
 
+	virtual void BeginPlay() override;
 	virtual void RestartPlayer(AController* NewPlayer) override;
 	virtual void Logout(AController* Exiting) override;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Agrarian|Persistence", meta = (ClampMin = "0"))
+	float ServerAutoSaveIntervalSeconds = 300.0f;
+
+protected:
+	void RunServerAutoSave();
+
+	FTimerHandle ServerAutoSaveTimerHandle;
 };