Initial commit: Vertical Partition Streaming plugin (UE 5.7)

Bounded vertical route partition / streaming for handcrafted spiral climb maps
(Only Up / Only Climb). Not World Partition, not Level Instances as core arch.

- Z-cell segmentation + optional XY subcells, editor builder + commandlet
- NonDestructive visibility backend + streaming-level backend
- Offline HLOD proxies: MergedMesh / SimplifiedProxy (ProxyLOD)
- Universal Level Instance + Packed Level Actor + HISM support (flatten+merge)
- Vertical-aware runtime streamer (full/preload/HLOD/unload, hysteresis,
  velocity prediction, fall-risk), WP-style debug viz + vp.* console
- Safe-by-default: only static decor streams; sky/lights/gameplay stay persistent

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Source/VerticalPartition/Public/VerticalPartitionManager.h

@@ -0,0 +1,62 @@
+// Copyright IHY. Vertical Partition Streaming plugin.
+//
+// In-world coordinator. One per streamed level (auto-spawned by the volume at
+// BeginPlay, or placed manually). Determines the tracked player's current cell,
+// drives the runtime subsystem at the configured interval, and hosts the debug
+// component. Keep this lightweight: the heavy lifting is in the subsystem.
+#pragma once
+
+#include "CoreMinimal.h"
+#include "GameFramework/Actor.h"
+#include "VerticalPartitionTypes.h"
+#include "VerticalPartitionManager.generated.h"
+
+class UVerticalPartitionDescriptor;
+class UVerticalPartitionDebugComponent;
+class AVerticalPartitionVolume;
+
+UCLASS()
+class VERTICALPARTITION_API AVerticalPartitionManager : public AActor
+{
+	GENERATED_BODY()
+
+public:
+	AVerticalPartitionManager();
+
+	/** Descriptor to stream. If unset, the manager searches the level for a volume. */
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category="VerticalPartition")
+	TSoftObjectPtr<UVerticalPartitionDescriptor> Descriptor;
+
+	/** Optional explicit volume (otherwise the first one found is used). */
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category="VerticalPartition")
+	TObjectPtr<AVerticalPartitionVolume> Volume;
+
+	/** Pawn whose position drives streaming. Defaults to local player pawn each tick. */
+	UPROPERTY(BlueprintReadWrite, Category="VerticalPartition")
+	TWeakObjectPtr<APawn> TrackedPawn;
+
+	UPROPERTY(VisibleAnywhere, Category="VerticalPartition")
+	TObjectPtr<UVerticalPartitionDebugComponent> DebugComponent;
+
+	virtual void BeginPlay() override;
+	virtual void EndPlay(const EEndPlayReason::Type EndPlayReason) override;
+	virtual void Tick(float DeltaSeconds) override;
+
+	/** Snap streaming to the tracked pawn immediately (checkpoint / teleport). */
+	UFUNCTION(BlueprintCallable, Category="VerticalPartition")
+	void RequestSnap() { bSnapNextUpdate = true; }
+
+	/** Teleport the tracked pawn to the centre of a Z cell (debug). */
+	UFUNCTION(BlueprintCallable, Category="VerticalPartition")
+	void TeleportToCell(int32 Z);
+
+private:
+	float UpdateAccumulator = 0.f;
+	bool bSnapNextUpdate = true;            // snap on the first update
+	bool bHavePrevPos = false;
+	FVector PrevTrackedPos = FVector::ZeroVector;
+	FVector SmoothedVelocity = FVector::ZeroVector;
+
+	APawn* ResolveTrackedPawn();
+	bool BuildContext(struct FVerticalStreamingContext& OutCtx, float DeltaSeconds, bool& bOutTeleport);
+};