Handle interrupted navigation transitions

src/lib/ui/motion/viewTransition.ts

@@ -2,8 +2,7 @@
 // browser's View Transitions API so route changes cross-fade cleanly and
 // shared-element transitions (Fleet card → Server detail hero) morph.
 //
-// Chromium ships the API today; Firefox and Safari fall through to a plain
-// navigation — same behavior as before, just without the transition.
+// Browsers without the API use ordinary navigation.
 
 // Structural type — accepts whatever SvelteKit passes to onNavigate without
 // coupling to a specific @sveltejs/kit version's type name.
@@ -13,15 +12,20 @@ export function enableViewTransitions(navigation: NavigationLike): Promise<void>
     // Feature-detect without a custom Document extension — the DOM lib type
     // varies between TS versions, and any narrowing has to survive both.
     const start = (document as unknown as {
-        startViewTransition?: (cb: () => void | Promise<void>) => unknown;
+        startViewTransition?: (cb: () => void | Promise<void>) => { ready: Promise<void>; finished: Promise<void> };
     }).startViewTransition;
 
     if (typeof start !== 'function') return;
 
     return new Promise<void>((resolve) => {
-        start.call(document, async () => {
-            resolve();
-            await navigation.complete;
-        });
+        try {
+            const transition = start.call(document, async () => {
+                resolve();
+                // Another navigation can supersede this one during its animation.
+                await navigation.complete.catch(() => {});
+            });
+            void transition.ready.catch(() => {});
+            void transition.finished.catch(() => {}).finally(resolve);
+        } catch { resolve(); }
     });
 }