internal/task: implement atomic primitives for preemptive scheduling

src/internal/task/atomic-preemptive.go

@@ -0,0 +1,14 @@
+//go:build scheduler.threads
+
+package task
+
+// Atomics implementation for non-cooperative systems (multithreaded, etc).
+// These atomic types use real atomic instructions.
+
+import "sync/atomic"
+
+type (
+	Uintptr = atomic.Uintptr
+	Uint32  = atomic.Uint32
+	Uint64  = atomic.Uint64
+)