fix psalm errors

src/Previous/Sockets/Client.php

@@ -178,6 +178,8 @@ public function timeoutAfter(Period $timeout): self
      * data provided by the callback and then restart watching for the socket
      * to be readable.
      *
+     * @psalm-mutation-free
+     *
      * @param callable(): Sequence<Str> $provide
      */
     public function heartbeatWith(callable $provide): self
@@ -200,6 +202,8 @@ public function heartbeatWith(callable $provide): self
      *
      * Use this method to abort the watch when you receive signals.
      *
+     * @psalm-mutation-free
+     *
      * @param callable(): bool $abort
      */
     public function abortWhen(callable $abort): self

src/Previous/Sockets/Server/Pool.php

@@ -43,6 +43,9 @@ public static function of(
         );
     }
 
+    /**
+     * @psalm-mutation-free
+     */
     public function with(Server $server): self
     {
         return new self(