fix: overlay preparation on tokio

crates/chain-state/src/deferred_trie.rs

@@ -312,6 +312,11 @@ impl DeferredTrieData {
     /// Given that invariant, circular wait dependencies are impossible.
     #[instrument(level = "debug", target = "engine::tree::deferred_trie", skip_all)]
     pub fn wait_cloned(&self) -> ComputedTrieData {
+        #[cfg(feature = "rayon")]
+        debug_assert!(
+            rayon::current_thread_index().is_none(),
+            "wait_cloned must not be called from a rayon worker thread"
+        );
         let mut state = self.state.lock();
         match &mut *state {
             // If the deferred trie data is ready, return the cached result.

crates/engine/tree/src/tree/mod.rs

@@ -1413,7 +1413,7 @@ where
         // Spawn a background task to trigger computation so it's ready when the next payload
         // arrives.
         if let Some(overlay) = self.state.tree_state.prepare_canonical_overlay() {
-            rayon::spawn(move || {
+            tokio::task::spawn_blocking(move || {
                 let _ = overlay.get();
             });
         }