ST6RI-823 Minor enhancements to the registrator workflow

 - Added error handling for the command registrator interface
 - Added Javadoc to the registrator to clarify the expected contract of
implementors

Author: ujhelyiz

org.omg.sysml.jupyter.kernel/src/main/java/org/omg/sysml/jupyter/kernel/IMagicCommandRegistrator.java

@@ -1,7 +1,7 @@
 /*****************************************************************************
  * SysML 2 Pilot Implementation
  * Copyright (c) 2025 Model Driven Solutions, Inc.
- *    
+ *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Lesser General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or
@@ -16,16 +16,31 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  *
  * @license LGPL-3.0-or-later <http://spdx.org/licenses/LGPL-3.0-or-later>
- * 
+ *
  * Contributors:
  *  Zoltan Ujhelyi, MDS
- * 
+ *
  *****************************************************************************/
 package org.omg.sysml.jupyter.kernel;
 
+import org.omg.sysml.interactive.SysMLInteractiveHelp;
+
 import io.github.spencerpark.jupyter.kernel.magic.registry.Magics;
 
 public interface IMagicCommandRegistrator {
 
+	/**
+	 * Implementors of this method are free to register their extra commands to the
+	 * Jupyter kernel. This method is called when the Jupyter environment is
+	 * initialized and it assumed the registration code will run quickly and without
+	 * exceptions. If the registrator cannot run successfully, it should not
+	 * register anything instead of throwing an exception.
+	 * </p>
+	 * Implementors are recommended to use the register methods of the {@link Magics}
+	 * class. Help is managed by the {@link SysMLInteractiveHelp} class.
+	 *
+	 * @see Magics#registerMagics(Class)
+	 * @see SysMLInteractiveHelp#registerHelpString(String, String, String)
+	 */
 	void registerMagicCommand(Magics magics);
 }

org.omg.sysml.jupyter.kernel/src/main/java/org/omg/sysml/jupyter/kernel/SysMLKernel.java

@@ -85,7 +85,17 @@ public SysMLKernel() {
         this.magics.registerMagics(Load.class);
         this.magics.registerMagics(ApiBasePath.class);
 
-		ServiceLoader.load(IMagicCommandRegistrator.class).forEach(reg -> reg.registerMagicCommand(this.magics));
+		ServiceLoader.load(IMagicCommandRegistrator.class).forEach(reg -> {
+			try {
+				reg.registerMagicCommand(this.magics);
+			} catch (Exception e) {
+				// Given there is no available logging mechanism and an exception thrown by the
+				// registrator would cause the Jupyter kernel not to start up correctly, errors
+				// are logged to the standard err output, but otherwise ignored.
+				System.err.printf("Error while running the command registrator %s: %s", reg.getClass().getTypeName(),
+						e.getMessage());
+			}
+		});
 
         this.magicParser = new MyMagicParser();
     }