Editor action `toggle-overwrite-mode`.
Run it from the command palette or a key binding via the action id `toggle_overwrite_mode`.
It is dispatched by `App::run_action("toggle_overwrite_mode")` and, for editing actions, backed
by `Editor::toggle_overwrite_mode` in `editor_core`. See `crates/vix-editor-core/spec/index.md` for the full
catalog.