fix(export): Include nested packages in SysML textual export

Add missing org.eclipse.syson.sysml.Package import in SysMLRelationPredicates.
Without this import, Package.class resolved to java.lang.Package instead of
org.eclipse.syson.sysml.Package, causing nested packages to be omitted from
the textual export output.

Author: vik378

CHANGELOG.adoc

@@ -119,6 +119,7 @@ And the following methods have been added:
 
 === Bug fixes
 
+- [export] Fix textual export not including nested packages in the output due to missing `org.eclipse.syson.sysml.Package` import in `SysMLRelationPredicates`.
 - https://github.com/eclipse-syson/syson/issues/1847[#1847] [export] Textual export duplicates "abstract" keyword for `OccurrenceUsage`.
 - https://github.com/eclipse-syson/syson/issues/1887[#1887] [export] Export fails to escape some names when using qualified name.
 - https://github.com/eclipse-syson/syson/issues/1953[#1953] [import] Fix an issue where `TransitionUsage` with `SendActionUsage` were not properly resolved.

backend/metamodel/syson-sysml-metamodel/src/main/java/org/eclipse/syson/sysml/textual/utils/SysMLRelationPredicates.java

@@ -28,6 +28,7 @@
 import org.eclipse.syson.sysml.MetadataUsage;
 import org.eclipse.syson.sysml.OccurrenceUsage;
 import org.eclipse.syson.sysml.OwningMembership;
+import org.eclipse.syson.sysml.Package;
 import org.eclipse.syson.sysml.ReferenceUsage;
 import org.eclipse.syson.sysml.Relationship;
 import org.eclipse.syson.sysml.SuccessionAsUsage;