ElyMark: renders asked of a failed page end at once (M-08)

The tally remembers why the page went down; until a load succeeds,
render() ends each new request with that reason instead of calling a
dead page. end_renders is a free function with a gpui test.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/ely-mark/src/view/tests.rs

@@ -0,0 +1,18 @@
+use std::{cell::RefCell, rc::Rc};
+
+use serde_json::Value;
+
+#[gpui::test]
+fn each_owed_render_ends_once_with_the_reason(cx: &mut gpui::TestAppContext) {
+    let got = Rc::new(RefCell::new(Vec::<(u8, Result<Value, String>)>::new()));
+    let pending = (0..2)
+        .map(|n| {
+            let got = got.clone();
+            Box::new(move |rendered, _: &mut gpui::App| got.borrow_mut().push((n, rendered))) as super::Rendered
+        })
+        .collect();
+    cx.update(|cx| super::end_renders(pending, "denied", cx));
+    cx.run_until_parked();
+    let denied = || Err("denied".to_string());
+    assert_eq!(*got.borrow(), [(0, denied()), (1, denied())]);
+}