Remove obsolete library cleanup and capability APIs

UnloadUnusedParts selects identities with zero references and calls the release
path, which immediately returns without changing them. Remove the no-op scan
and its model, project and preview callers, including the now-unused LoadLDD
library local. Actual last-reference unload and temporary identity cleanup remain
in their existing lifetime paths.

SupportsStudStyle always returns true. Remove the method and the unreachable
preferences branch that disables the stud-style selector.

Validation: warning-free macOS Qt 6.10 Debug build, all 45 offscreen lifecycle
checks and diff whitespace checks pass. No remaining references to either API.

common/lc_library.cpp

@@ -2080,15 +2080,6 @@ lcMesh* lcPiecesLibrary::GetLoadingMesh() const
 	return mLoadingMesh.get();
 }
 
-void lcPiecesLibrary::UnloadUnusedParts()
-{
-	for (lcPieceData* PieceData : mPieceManager->GetLibraryPieceData())
-	{
-		if (PieceData->GetRefCount() == 0 && PieceData->mState != lcAssetState::Unloaded)
-			ReleasePieceData(PieceData);
-	}
-}
-
 void lcPiecesLibrary::AddTextureReference(lcTexture* Texture)
 {
 	mTextureManager->AddTextureReference(Texture);
@@ -2099,11 +2090,6 @@ void lcPiecesLibrary::ReleaseTexture(lcTexture* Texture)
 	mTextureManager->ReleaseTexture(Texture);
 }
 
-bool lcPiecesLibrary::SupportsStudStyle() const
-{
-	return true;
-}
-
 void lcPiecesLibrary::UpdateStudStyleAndColors(lcStudStyle StudStyle, bool StudCylinderColorEnabled)
 {
 	Q_ASSERT(QThread::currentThread() == thread());

common/lc_library.h

@@ -160,8 +160,6 @@ public:
 	// Reloads the configured colors and updates the loading mesh.
 	void LoadColors();
 
-	bool SupportsStudStyle() const;
-
 	lcStudStyle GetStudStyle() const
 	{
 		return mStudStyle;
@@ -304,9 +302,6 @@ public:
 		return { mVertexBuffer, mIndexBuffer };
 	}
 
-	// Checks unused library parts under the existing zero-reference release policy.
-	void UnloadUnusedParts();
-
 	// Returns the borrowed placeholder mesh for pending or failed piece geometry.
 	lcMesh* GetLoadingMesh() const;
 

common/lc_mainwindow.cpp

@@ -2595,7 +2595,6 @@ void lcMainWindow::NewProject()
 
 	Project* NewProject = new Project();
 	gApplication->SetProject(NewProject);
-	lcGetPiecesLibrary()->UnloadUnusedParts();
 }
 
 bool lcMainWindow::OpenProject(const QString& FileName)

common/lc_model.cpp

@@ -1052,7 +1052,6 @@ void lcModel::LoadLDraw(QIODevice& Device, Project* Project)
 
 	mCurrentStep = CurrentStep;
 	CalculateStep(mCurrentStep);
-	Library->UnloadUnusedParts();
 
 	delete Piece;
 	delete Camera;
@@ -1299,7 +1298,6 @@ bool lcModel::LoadBinary(lcFile* file)
 	}
 
 	CalculateStep(mCurrentStep);
-	lcGetPiecesLibrary()->UnloadUnusedParts();
 
 	return true;
 }
@@ -1322,9 +1320,7 @@ bool lcModel::LoadLDD(const QString& FileData)
 			Piece->SetGroup(NewGroup);
 	}
 
-	lcPiecesLibrary* Library = lcGetPiecesLibrary();
 	CalculateStep(mCurrentStep);
-	Library->UnloadUnusedParts();
 
 	return true;
 }
@@ -1361,8 +1357,6 @@ bool lcModel::LoadInventory(const std::vector<lcSetInventoryItem>& SetInventory)
 	if (!Library->WaitForPieceData(RequiredPieceData))
 		return false;
 
-	Library->UnloadUnusedParts();
-
 	auto RoundBounds = [](float& Value)
 	{
 		Value = ((Value < 0.0f) ? floor((Value - 5.0f) / 10.0f) : ceil((Value + 5.0f) / 10.0f)) * 10.0f;

common/lc_previewwidget.cpp

@@ -336,7 +336,6 @@ void lcPreview::ClearPreview()
 	lcPiecesLibrary* Library = lcGetPiecesLibrary();
 
 	Library->RemoveTemporaryPieceData();
-	Library->UnloadUnusedParts();
 	Redraw();
 }
 

qt/lc_qpreferencesdialog.cpp

@@ -236,9 +236,6 @@ lcPreferencesDialog::lcPreferencesDialog(QWidget* Parent, lcPreferencesDialogOpt
 	else
 		ui->PreviewViewSphereSizeCombo->setCurrentIndex(0);
 
-	if (!lcGetPiecesLibrary()->SupportsStudStyle())
-		ui->studStyleCombo->setEnabled(false);
-
 	ui->studStyleCombo->setCurrentIndex(static_cast<int>(mOptions->StudStyle));
 
 	ui->ShadingMode->setCurrentIndex(static_cast<int>(mOptions->Preferences.mShadingMode));