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/VerticalPartitionEditor/Public/VerticalPartitionCommandlet.h

@@ -0,0 +1,20 @@
+// Copyright IHY. Vertical Partition Streaming plugin (editor module).
+//
+// Offline build entry point:
+//   UnrealEditor-Cmd.exe Project.uproject -run=VerticalPartition -Map=/Game/Maps/MyMap
+#pragma once
+
+#include "CoreMinimal.h"
+#include "Commandlets/Commandlet.h"
+#include "VerticalPartitionCommandlet.generated.h"
+
+UCLASS()
+class UVerticalPartitionCommandlet : public UCommandlet
+{
+	GENERATED_BODY()
+
+public:
+	UVerticalPartitionCommandlet();
+
+	virtual int32 Main(const FString& Params) override;
+};