qa: swept ground transect closes the traversal release check

84 samples across the north sidewalk, carriageway and south sidewalk
(X -14900..-9420) come back with 0 holes and ground Z 317..395, so the
block is traversable rather than merely spawnable.

TODO: sidewalks/collision item now records the collision state and what
is genuinely left (kerb radii, aprons, kerb-height assumption); the
traversal release check is ticked with the measurement.

Game/GigLine/Source/GigLine/GigLineCharacter.cpp

@@ -297,8 +297,42 @@ void AGigLineCharacter::StartQASelfTest()
 					State->bUnpausedBack ? TEXT("PASS") : TEXT("FAIL"));
 			}
 
-			// 6.0: verdict, then stop ticking.
-			if (E >= 6.0f)
+			// 6.0: ground transect - sweep both sidewalks and the carriageway and
+			// count holes, so "can traverse the block without falling through"
+			// is measured rather than assumed.
+			if (E >= 6.0f && State->Step < 7.0f)
+			{
+				State->Step = 7.0f;
+				UWorld* W = GetWorld();
+				int32 Holes = 0, Samples = 0;
+				float Lowest = 1.0e9f, Highest = -1.0e9f;
+				static const float Lanes[] = {-1400.0f, -167.0f, 1000.0f}; // N walk, road, S walk
+				for (float LaneY : Lanes)
+				{
+					for (float X = -14900.0f; X <= -9420.0f; X += 200.0f)
+					{
+						FHitResult Hit;
+						FCollisionQueryParams Q(TEXT("GigLineTransect"), false, this);
+						const bool bHit = W->LineTraceSingleByChannel(Hit,
+							FVector(X, LaneY, 3000.f), FVector(X, LaneY, -3000.f),
+							ECC_Visibility, Q);
+						++Samples;
+						if (!bHit)
+						{
+							++Holes;
+							continue;
+						}
+						Lowest = FMath::Min(Lowest, Hit.ImpactPoint.Z);
+						Highest = FMath::Max(Highest, Hit.ImpactPoint.Z);
+					}
+				}
+				UE_LOG(LogTemp, Log,
+					TEXT("GigLine QA: transect %d samples, %d holes, ground Z %.0f..%.0f -> %s"),
+					Samples, Holes, Lowest, Highest, Holes == 0 ? TEXT("PASS") : TEXT("FAIL"));
+			}
+
+			// 7.0: verdict, then stop ticking.
+			if (E >= 7.0f)
 			{
 				const bool bAllPass = State->bWalkMoved && State->bResetReturned
 					&& State->bPausedOn && State->bUnpausedBack;