Enable 4x MSAA anti-aliasing for the GL viewport

Request a multisampled framebuffer via the openglfx GLCanvas msaa parameter
and enable GL_MULTISAMPLE, smoothing jagged polygon/line/point edges. The
picking framebuffer stays single-sample so picked ids remain exact.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CityDoctorParent/Extensions/CityDoctorGUI/src/main/java/de/hft/stuttgart/citydoctor2/gui/gl/GLViewport.java

@@ -55,7 +55,8 @@ public class GLViewport {
     private double lastY;
 
     public GLViewport() {
-        canvas = new GLCanvas(new JOGLExecutor(), GLProfile.CORE);
+        // args: executor, profile, flipY=false, msaa=4 -> request a 4x multisampled framebuffer for AA
+        canvas = new GLCanvas(new JOGLExecutor(), GLProfile.CORE, false, 4);
         canvas.addOnInitEvent(ev -> {
             // GL context (re)created: shaders/buffers from any previous context are gone. Drop our
             // handles and re-queue the current scene so it is re-uploaded into the new context.
@@ -115,6 +116,7 @@ public class GLViewport {
             pickProgram = new ShaderProgram(gl, "pick.vert", "pick.frag");
             overlay.init(gl);
             gl.glEnable(GL.GL_DEPTH_TEST);
+            gl.glEnable(GL.GL_MULTISAMPLE); // anti-aliasing for the multisampled framebuffer
             initialized = true;
         }