Fix Flaky PID Retrieval (#296)

* testing circuit breaker

* update lock

* update docs

* improve PID management in Session class

* revert circuit and queue changes

* use wait for in the test

* Fix race condition for PID retrieval

Updated the changeset to fix a race condition during PID retrieval.

Author: whoiskatrin

.changeset/clean-pans-switch.md

@@ -0,0 +1,5 @@
+---
+"@cloudflare/sandbox": patch
+---
+
+fix race condition for PID retrieval 

package-lock.json

@@ -151,6 +151,7 @@ export class ProcessService {
         async (event) => {
           // Route events to process record listeners
           if (event.type === 'start' && event.pid !== undefined) {
+            processRecord.pid = event.pid;
             await this.store.update(processRecord.id, { pid: event.pid });
           } else if (event.type === 'stdout' && event.data) {
             processRecord.stdout += event.data;