Add SPA session validation and buglist, update migration docs

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Co-Authored-By: Claude <noreply@anthropic.com>

node_modules/playwright/lib/runner/workerHost.js

@@ -79,6 +79,9 @@ class WorkerHost extends import_processHost.ProcessHost {
   runTestGroup(runPayload) {
     this.sendMessageNoReply({ method: "runTestGroup", params: runPayload });
   }
+  async sendCustomMessage(payload) {
+    return await this.sendMessage({ method: "customMessage", params: payload });
+  }
   hash() {
     return this._hash;
   }