fix: ensure task::spawn maintains reactive ownership (closes #4203) (#4206)

leptos/src/lib.rs

@@ -301,12 +301,17 @@ pub mod logging {
 /// Utilities for working with asynchronous tasks.
 pub mod task {
     use any_spawner::Executor;
+    use reactive_graph::computed::ScopedFuture;
     use std::future::Future;
 
     /// Spawns a thread-safe [`Future`].
+    ///
+    /// This will be run with the current reactive owner and observer using a [`ScopedFuture`].
     #[track_caller]
     #[inline(always)]
     pub fn spawn(fut: impl Future<Output = ()> + Send + 'static) {
+        let fut = ScopedFuture::new(fut);
+
         #[cfg(not(target_family = "wasm"))]
         Executor::spawn(fut);