plugin.gd now checks Engine.get_version_info() in _enter_tree and pushes a
loud error if the engine is older than 4.6. Doesn't actually disable the
addon's class_names (Godot parses those independently of EditorPlugin), but
gives users a clear "this is the cause" signal before any cryptic downstream
errors land.
Also removes four add_autoload_singleton calls for gd-options-owned scripts
(GameSettings, InputSettings, GraphicsSettings, AudioSettings). They were
copy-paste leftovers from when this addon was forked; gd-options/plugin.gd
already registers them, so this addon was double-registering — gd-dynamic-
sound has no business owning those autoloads.
README documents the 4.6 requirement near the top.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>