Expose scheduler state and don't enqueue/trigger midi keys when repl stopped

packages/core/schedulerState.mjs

@@ -8,6 +8,7 @@ let time;
 let cpsFunc;
 let pattern;
 let triggerFunc;
+let isStarted;
 export function getTime() {
   if (!time) {
     throw new Error('no time set! use setTime to define a time source');
@@ -42,3 +43,11 @@ export function setTriggerFunc(func) {
 export function getTriggerFunc() {
   return triggerFunc;
 }
+
+export function setIsStarted(val) {
+  isStarted = !!val;
+}
+
+export function getIsStarted() {
+  return isStarted;
+}