Document OpenGL 3D view in changelog

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

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Changed
+- Replaced the JavaFX-based 3D view with an OpenGL renderer (openglfx/JOGL) for smooth display of
+  large city models. Picking is now GPU-based; the 3D view requires OpenGL 3.3 (Windows/Linux).
+
 ## [3.18.3] (2026-04-16)
 
 ### Fixes