Simplify model metadata updates and discovery names

Update model filenames and descriptions directly in SetModel, removing
metadata-only forwarding through the library and piece manager. Registry
renames remain synchronized in the manager.

Reuse the bounded piece-name normalizer for archive and directory discovery
to remove duplicated conversion loops and avoid writing a terminator past
the name buffer. Preserve original source filenames and archive offsets.

Validated with a warning-free Qt 6.10 Debug build and all 51 offscreen
lifecycle groups; diff whitespace checks pass.

common/lc_piecedata.cpp

@@ -115,7 +115,9 @@ void lcPieceData::SetModel(lcModel* Model)
 		lcGetPiecesLibrary()->ClearPieceDataLoadError(this);
 	}
 
-	lcGetPiecesLibrary()->SetModelPieceDataName(this, Model->GetProperties().mFileName.toLatin1().data());
+	const QByteArray Name = Model->GetProperties().mFileName.toLatin1();
+	lcstrcpy(mFileName, Name.constData());
+	lcstrcpy(m_strDescription, Name.constData());
 }
 
 void lcPieceData::CreateProject(Project* NewProject, const char* PieceName)