fix(input): restore working controls + add input harness + build fixes

Consolidated from the qa-input-collision-fix-0.1.0 work, applied onto main so
only the changes main genuinely lacks are carried (main already merged the
walkable-demo/collision work independently).

- fix(input): populate the UE 5.8 FInputMappingContextMappingData
  DefaultKeyMappings field in ue_create_input_assets.py (the runtime reads
  GetMappings()->DefaultKeyMappings.Mappings; the script previously wrote only
  the deprecated 'mappings' array, so the cooked game had 0 runtime mappings
  and every key silently did nothing — in packaged AND PIE). Regenerated
  IMC_Default.uasset. WASD/mouse/Space/R/Escape verified working.
- fix(build): drop editor-only APIs that break the game target build —
  UStaticMesh::PostEditChange() (GigLineAssetTools) and AActor::GetActorLabel()
  (character ground probe). GigLine and GigLineEditor now both compile clean.
- tools: OS-level uinput input harness (input_emulation.py + input_test.py) and
  run_pie.sh for PIE isolation; document the PIE-vs-packaged input test in
  Docs/build.md. Removed the temporary SIM/EI/screenshot diagnostics from the
  character.

Game/GigLine/Source/GigLine/GigLineAssetTools.cpp

@@ -21,7 +21,9 @@ void UGigLineAssetTools::SetComplexCollisionAsSimple(UStaticMesh* Mesh, bool bEn
 	BodySetup->InvalidatePhysicsData();
 	BodySetup->CreatePhysicsMeshes();
 	Mesh->MarkPackageDirty();
-	Mesh->PostEditChange();
+	// PostEditChange() is editor-only and not a member of UStaticMesh; the
+	// physics data regeneration above plus MarkPackageDirty is all a headless
+	// commandlet needs to persist the new collision flags.
 }
 
 void UGigLineAssetTools::ClearSimpleCollision(UStaticMesh* Mesh)
@@ -41,7 +43,6 @@ void UGigLineAssetTools::ClearSimpleCollision(UStaticMesh* Mesh)
 	BodySetup->InvalidatePhysicsData();
 	BodySetup->CreatePhysicsMeshes();
 	Mesh->MarkPackageDirty();
-	Mesh->PostEditChange();
 }
 
 FString UGigLineAssetTools::GetCollisionComplexity(UStaticMesh* Mesh)

Game/GigLine/Source/GigLine/GigLineCharacter.cpp

@@ -157,46 +157,6 @@ void AGigLineCharacter::BeginPlay()
 		PC->bShowMouseCursor = false;
 	}
 
-	// TEMP QA: one screenshot at +1.5s so the actual frame is reviewable.
-	FTimerHandle ShotHandle;
-	GetWorldTimerManager().SetTimer(ShotHandle, [this]()
-	{
-		if (APlayerController* PC = Cast<APlayerController>(GetController()))
-		{
-			PC->ConsoleCommand(TEXT("HighResShot 1280x720"));
-		}
-	}, 1.5f, false);
-
-	// TEMP QA: every second log world time + capsule Z + gravity + fall state so
-	// we can see whether the world is simulating the pawn at all (symptom:
-	// "spawns above ground but never falls, no input").
-	FTimerHandle SimHandle;
-	GetWorldTimerManager().SetTimer(SimHandle, [this]()
-	{
-		UCharacterMovementComponent* M = GetCharacterMovement();
-		UE_LOG(LogTemp, Log,
-			TEXT("GigLine SIM: t=%.2f XYZ=(%.0f,%.0f,%.0f) grav=%.1f fall=%d local=%d role=%d mode=%d ctrl=%s"),
-			GetWorld() ? GetWorld()->GetTimeSeconds() : -1.f,
-			GetActorLocation().X, GetActorLocation().Y, GetActorLocation().Z,
-			M ? M->GetGravityZ() : 0.f,
-			(M && M->IsFalling()) ? 1 : 0,
-			IsLocallyControlled() ? 1 : 0,
-			(int)GetLocalRole(),
-			M ? (int)M->MovementMode : -1,
-			GetController() ? *GetController()->GetName() : TEXT("NONE"));
-		if (UWorld* W = GetWorld())
-		{
-			const FVector L = GetActorLocation();
-			FHitResult Hit;
-			FCollisionQueryParams Q(TEXT("GigLineGroundProbe"), false, this);
-			const bool bHit = W->LineTraceSingleByChannel(Hit,
-				FVector(L.X, L.Y, 3000.f), FVector(L.X, L.Y, -3000.f), ECC_Visibility, Q);
-			UE_LOG(LogTemp, Log, TEXT("GigLine GROUND: top=%.0f actor=%s"),
-				bHit ? Hit.ImpactPoint.Z : -9999.f,
-				bHit && Hit.GetActor() ? *Hit.GetActor()->GetActorLabel() : TEXT("none"));
-		}
-	}, 1.0f, true);
-
 	if (FParse::Param(FCommandLine::Get(), TEXT("qaselftest")))
 	{
 		StartQASelfTest();
@@ -428,8 +388,6 @@ namespace
 
 void AGigLineCharacter::MoveForward(const FInputActionValue& Value)
 {
-	UE_LOG(LogTemp, Log, TEXT("GigLine IN: MoveForward fired, axis=%.3f type=%d"),
-		FMath::Abs(SignedAxis(Value, false)), (int)Value.GetValueType());
 	ApplyMove(FMath::Abs(SignedAxis(Value, false)), 0.0f);
 }
 
@@ -453,8 +411,6 @@ void AGigLineCharacter::ApplyMove(float Forward, float Strafe)
 	const AController* Controller = GetController();
 	if (!Controller)
 	{
-		UE_LOG(LogTemp, Log, TEXT("GigLine IN: ApplyMove called but NO controller (fwd %.2f strafe %.2f)"),
-			Forward, Strafe);
 		return;
 	}
 	if (FMath::IsNearlyZero(Forward) && FMath::IsNearlyZero(Strafe))
@@ -468,8 +424,6 @@ void AGigLineCharacter::ApplyMove(float Forward, float Strafe)
 
 	AddMovementInput(ForwardDir, Forward);
 	AddMovementInput(RightDir, Strafe);
-	UE_LOG(LogTemp, Log, TEXT("GigLine IN: ApplyMove fwd %.2f strafe %.2f controller=%s yaw=%.0f"),
-		Forward, Strafe, *Controller->GetName(), Controller->GetControlRotation().Yaw);
 }
 
 void AGigLineCharacter::Look(const FInputActionValue& Value)