refactor(sheets, settings): drop the last sheet-ring remnants and dead settings

The far sheet ring was already gone from the runtime; this removes what
was left of it:
- UVoxelSettings::bFarSheetRing / FarSheetSpanLevels, the
  voxel.TestFarSheetRing switch, and their log/trace/dump fields.
- The sheet branch of VoxelClipmapDesiredTiles (FParameters sheet fields,
  OuterShell sheet level, sheet ring emission). Output for the runtime
  configuration (sheet off) is unchanged: same rings, same alignment.
- Tests: VerticalStrateReach now asserts the sheet-free selector (its
  expected counts were stale since the aligned-ring change 85a803b:
  LOD0 343 -> 512); ClipmapNoOverlap drops the sheet sweep cases and the
  frozen 7486c29 oracle's sheet branch. New expected values were computed
  with a Python port of the selector that reproduces the test's existing
  635/594487 and 508/74295 measurements exactly; all 5,145 sweep cases
  pass (no overlap, full coverage).
- Tools/VoxelForgeTest.ps1 no longer passes voxel.TestFarSheetRing or
  reports far_sheet_ring. The sheet_tile dump field is kept (the parity
  compare reads it).

Also removes settings nothing reads: CeilingViewMultiplier,
CeilingBandChunks (pre-clipmap ceiling band) and DensityVolumeMaxTasks
(the volume fill runs on its own thread). Saved assets that still carry
these values load normally; the values are ignored.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01URDGLsu7c4nunqNFPJEFPU

Source/VoxelForge/Public/VoxelSettings.h

@@ -123,21 +123,6 @@ public:
 		return FMath::Clamp(FMath::Max(StrateContentCutMinLevel, 1), 1, 9);
 	}
 
-	// Open-world SKY reach: the sky-cap ceiling of an open strate (SurfaceWorld / FloatingIslands)
-	// is FAR, so the ceiling BAND is streamed across a wider horizontal radius = ViewDistanceXY ×
-	// this, so the sky reaches toward the horizon instead of being a patch over the player's head.
-	// Only the ceiling band (top CeilingBandChunks of the strate) gets the wide radius — the empty
-	// air below it stays at base XY. Cost grows ~ multiplier² (more far chunks/draws; gen is cheap
-	// and batching keeps the game-thread cost low). 1 = off. Live-tunable on the asset — push to 4
-	// if the draw budget allows; a proper to-the-horizon view (terrain too) is the chunk-LOD clipmap.
-	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Voxel|Streaming", meta = (ClampMin = "1"))
-	int32 CeilingViewMultiplier = 2;
-
-	// How many chunks down from the strate top get the wide CeilingViewMultiplier radius (covers
-	// the sky-cap slab). Bigger = no gaps if the ceiling surface dips, but more far chunks.
-	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Voxel|Streaming", meta = (ClampMin = "1"))
-	int32 CeilingBandChunks = 4;
-
 	//=========================================================================
 	// CLIPMAP (chunked-LOD streaming — supersedes the ViewDistance box above)
 	//=========================================================================
@@ -183,16 +168,6 @@ public:
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Voxel|Clipmap", meta = (ClampMin = "0"))
 	int32 RenderDistanceChunks = 768;
 
-	// UNUSED: the far sheet ring was removed from the runtime; the render-distance ring is always
-	// marching-cubes tiles at MaxClipLevel. Kept only so saved assets and the test harness's
-	// `voxel.TestFarSheetRing` switch still load; it has no effect.
-	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Voxel|Clipmap")
-	bool bFarSheetRing = false;
-
-	// UNUSED (see bFarSheetRing). Kept so saved assets still load; it has no effect.
-	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Voxel|Clipmap", meta = (ClampMin = "1", ClampMax = "4", EditCondition = "bFarSheetRing"))
-	int32 FarSheetSpanLevels = 2;
-
 	// SKIRTS — seal the thin cracks where neighbouring clipmap shells (different resolutions) meet.
 	// A short wall is extruded into the solid from each surface edge on the tile's outer faces.
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Voxel|Clipmap")
@@ -336,12 +311,6 @@ public:
 	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Voxel|Lighting", meta = (ClampMin = "1", ClampMax = "5"))
 	int32 DensityVolumeLevels = 3;
 
-	// DEPRECATED / unused: the volume fill no longer runs on the shared UE::Tasks pool (where it
-	// starved behind mesh-gen). It now runs on ONE dedicated thread off the pool, so there's no task
-	// budget to cap. Kept only so existing saved assets don't error; safe to ignore.
-	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Voxel|Lighting", meta = (ClampMin = "1", ClampMax = "16"))
-	int32 DensityVolumeMaxTasks = 4;
-
 	// A fill box is split into Z-slabs of at most this many cells per task, so no single task is
 	// huge (a full level refill on startup/teleport fans out across workers). Lower = more, smaller
 	// tasks (better parallelism / latency); higher = fewer, fatter tasks.