wip(tunnels): continuous world-core sweep, slope in degrees, bounded winding -- NOT MERGED: +18-30% worker CPU, visuals unconfirmed

Tunnel round from the owner's playtest. Luna's ablations traced the ribs to the world-space tunnel-core stage: disabling it removes them, while terracing, detail ops, roughness, the support floor, lateral warp, radius jitter, winding and LOD do not. The per-span capsule union is replaced by a deterministic Catmull-Rom sweep. Winding and graph expansion are now gated on bTunnelFloorEnabled (they ran even with the floor off). TunnelFloorGentleSlopeThreshold is authored in degrees (0-90, min 1 deg, DetSinCos conversion, legacy tangent values migrated: 0.3 -> 16.7 deg). The route length is capped at 6 waves x 640 = 3840 voxels, so 0.1 deg loads instead of freezing (2048 collapsed canonical reach; 24576 used ~2 GB). Room-wall trimming is behind voxel.TunnelMouthTrim (default OFF): with it on, a 36 m gap disconnects the walk.

Canonical walk: 20,907 / 10,981, connected (was 20,830 / 10,909); exports identical with -voxel.CrtFma3=0; TilePostReachProof, DetSinCos and strate crossing pass. NOT merged because: one S/M pair vs the tip DLL shows worker CPU +17.8% static / +30.3% moving and worse p95; and the orchestrator's look at the before/after renders is inconclusive (camera not matched; regular grooves still visible in the after interior). Next: owner checks the look in game; if smooth, make the sweep cheap before merging; if not, drop the sweep and keep the degrees/bound/wind-gate parts.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

Source/VoxelForge/Private/VoxelStrateComposer.cpp

@@ -1139,7 +1139,7 @@ namespace
             if (FieldName == TEXT("TunnelEndpointZOffset")) return Set(0.0f, 1.0f);
             if (FieldName == TEXT("TunnelFloorTerraceStepHeight")) return Set(0.25f, FMath::Max(2.0f, HQuarter));
             if (FieldName == TEXT("TunnelFloorMaxLedgeHeight")) return Set(1.0f, FMath::Max(4.0f, HQuarter));
-            if (FieldName == TEXT("TunnelFloorGentleSlopeThreshold")) return Set(0.0f, 1.5f);
+            if (FieldName == TEXT("TunnelFloorGentleSlopeThreshold")) return Set(0.0f, 90.0f);
             if (FieldName == TEXT("SDFBlendRadius")) return Set(2.0f, FMath::Max(4.0f, H * 0.15f));
             if (FieldName == TEXT("WaterLevelRelative")) return Set(0.0f, 1.0f);
             if (FieldName == TEXT("CaveWarpStrength")) return Set(0.0f, HHalf);