T44d Web · Gallery builds for wasm32: one story per section by URL, themed by the host

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.

examples/gallery/pages/finance/assets.rs

@@ -1,4 +1,4 @@
-use std::time::{Duration, Instant};
+use std::time::Duration;
 
 use ely_gpui_component::{
     charts::PieChart,
@@ -13,6 +13,7 @@ use ely_gpui_component::{
 };
 use gpui::{App, IntoElement, ParentElement, SharedString, Styled, Window, div, px};
 use jiff::{Timestamp, civil::date, tz::TimeZone};
+use web_time::Instant;
 
 use crate::ui::{keep, noise, row, section, set};