The gallery's entry runs natively or, on wasm32, from a wasm_bindgen start through gpui_web, single-threaded with WebGL2 fallback. ?page, ?story and ?theme choose what shows; an unknown one fails in the page and the log. set_theme switches the mode later. Pictures load from ELY_GALLERY_ASSETS. scripts/stories.py writes examples/gallery/stories.json from the pages.