fix(rpc): incorrect constructor return type (#16084)

The constructor `NewStateRootNotFoundError` incorrectly returned
`StateNotFoundError`. This prevented handlers that rely on
errors.As(err, *lookup.StateRootNotFoundError) from matching and mapping
the error to HTTP 404. The function now returns
StateRootNotFoundError and constructs that type, restoring the intended
behavior for “state root not found” cases.

---------

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

beacon-chain/rpc/lookup/stater.go

@@ -82,8 +82,8 @@ type StateRootNotFoundError struct {
 }
 
 // NewStateRootNotFoundError creates a new error instance.
-func NewStateRootNotFoundError(stateRootsSize int) StateNotFoundError {
-	return StateNotFoundError{
+func NewStateRootNotFoundError(stateRootsSize int) StateRootNotFoundError {
+	return StateRootNotFoundError{
 		message: fmt.Sprintf("state root not found in the last %d state roots", stateRootsSize),
 	}
 }

changelog/Snezhkko_fix-type.md

@@ -0,0 +1,3 @@
+## Fixed
+
+- incorrect constructor return type [#16084](https://github.com/OffchainLabs/prysm/pull/16084)