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/probe.rs

@@ -12,6 +12,7 @@ pub struct Probes(HashMap<&'static str, Bounds<Pixels>>);
 impl Global for Probes {}
 
 impl Probes {
+    #[cfg(not(target_family = "wasm"))]
     pub fn get(key: &str, cx: &App) -> Option<Bounds<Pixels>> {
         cx.try_global::<Probes>()
             .and_then(|probes| probes.0.get(key).copied())
@@ -39,10 +40,12 @@ impl Opened {
         cx.default_global::<Opened>().0.insert(key, handle);
     }
 
+    #[cfg(not(target_family = "wasm"))]
     pub fn take(key: &str, cx: &mut App) -> Option<AnyWindowHandle> {
         cx.default_global::<Opened>().0.remove(key)
     }
 
+    #[cfg(not(target_family = "wasm"))]
     pub fn get(key: &str, cx: &App) -> Option<AnyWindowHandle> {
         cx.try_global::<Opened>()
             .and_then(|opened| opened.0.get(key).copied())