Make highlight edges win depth ties so they show in wireframe

Highlight edges share the exact depth of the wireframe mesh lines, so GL_LESS
rejected them and they vanished in wireframe mode. Draw the overlay with
GL_LEQUAL (restored to GL_LESS afterward) so coincident markers draw on top
while still being occluded by nearer geometry.

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

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

@@ -198,6 +198,9 @@ public class GLViewport {
         scene.draw(gl);
         // wireframe applies to the geometry only; highlight markers always render filled
         gl.glPolygonMode(GL.GL_FRONT_AND_BACK, GL3.GL_FILL);
+        // highlight markers sit at the same depth as geometry edges (and the wireframe lines); use
+        // LEQUAL so the later-drawn markers win depth ties instead of being rejected by GL_LESS
+        gl.glDepthFunc(GL.GL_LEQUAL);
         // edge markers reuse the flat scene program (pos + colour)
         overlay.drawLines(gl, lineScale);
         // vertex markers use the sphere-impostor program (geometry shader -> camera-facing quads)
@@ -206,6 +209,7 @@ public class GLViewport {
         gl.glUniform2f(pointProgram.uniform(gl, "uViewport"), (float) w, (float) h);
         gl.glUniform1f(pointProgram.uniform(gl, "uPointSize"), pointScale);
         overlay.drawPoints(gl);
+        gl.glDepthFunc(GL.GL_LESS); // restore for the next frame's scene pass
 
         double[] req = pickRequest;
         if (req != null && currentScene != null) {