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/VerticalPartitionVolume.h

@@ -0,0 +1,89 @@
+// Copyright IHY. Vertical Partition Streaming plugin.
+//
+// The authoring volume. Drop one around the whole playable spiral, tune the
+// settings, and press Build. Bounds come from a UBoxComponent so they are trivial
+// to read at both editor and runtime (no BSP brush).
+#pragma once
+
+#include "CoreMinimal.h"
+#include "GameFramework/Actor.h"
+#include "VerticalPartitionTypes.h"
+#include "VerticalPartitionVolume.generated.h"
+
+class UBoxComponent;
+class UVerticalPartitionDescriptor;
+class AVerticalPartitionVolume;
+
+/**
+ * Decouples the runtime volume from the editor-only builder. The editor module
+ * installs Handler in StartupModule; the volume's CallInEditor buttons and the
+ * vp.* build console commands route through it. Lives in the runtime module so the
+ * volume can reference it, but is only ever populated in editor builds.
+ */
+struct VERTICALPARTITION_API FVerticalPartitionEditorBridge
+{
+#if WITH_EDITOR
+	static TFunction<void(AVerticalPartitionVolume*, EVerticalPartitionAction)> Handler;
+	static void Execute(AVerticalPartitionVolume* Volume, EVerticalPartitionAction Action)
+	{
+		if (Handler) { Handler(Volume, Action); }
+	}
+#endif
+};
+
+UCLASS(HideCategories=(Collision, Physics, Navigation, HLOD, Input, Replication))
+class VERTICALPARTITION_API AVerticalPartitionVolume : public AActor
+{
+	GENERATED_BODY()
+
+public:
+	AVerticalPartitionVolume();
+
+	/** Box that defines the bounded playable region to partition. */
+	UPROPERTY(VisibleAnywhere, BlueprintReadOnly, Category="VerticalPartition")
+	TObjectPtr<UBoxComponent> Box;
+
+	/** Per-volume settings (seeded from project defaults on placement). */
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category="VerticalPartition", meta=(ShowOnlyInnerProperties))
+	FVerticalPartitionSettings Settings;
+
+	/** Descriptor produced by Build; consumed by the runtime manager. */
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category="VerticalPartition")
+	TSoftObjectPtr<UVerticalPartitionDescriptor> Descriptor;
+
+	/** World-space bounds of the volume (box transform * extent). */
+	UFUNCTION(BlueprintPure, Category="VerticalPartition")
+	FBox GetVolumeBounds() const;
+
+	virtual void OnConstruction(const FTransform& Transform) override;
+
+#if WITH_EDITOR
+	// ---- Detail-panel buttons (mirror the editor tool window) ----
+	UFUNCTION(CallInEditor, Category="Vertical Partition|1 - Analyze")
+	void AnalyzeCurrentLevel();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|2 - Build")
+	void BuildVerticalPartition();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|2 - Build")
+	void RebuildChangedCells();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|2 - Build")
+	void RebuildHLOD();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|3 - Validate")
+	void ValidateCells();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|3 - Validate")
+	void PreviewChunks();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|3 - Validate")
+	void SpawnHLODPreview();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|3 - Validate")
+	void ClearPreview();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|4 - Commit")
+	void CommitConversion();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|4 - Commit")
+	void RestoreFromBackup();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|5 - Maintenance")
+	void ClearGeneratedData();
+	UFUNCTION(CallInEditor, Category="Vertical Partition|5 - Maintenance")
+	void DumpReport();
+
+	virtual void PostEditChangeProperty(FPropertyChangedEvent& PropertyChangedEvent) override;
+#endif
+};