Wait for browser to load before sending messages

[PHPirates]

Previous solution was blocking the UI and not working, with exception:

2026-06-30 20:49:02,765 [   2789] SEVERE - #com.firsttimeinforever.intellij.pdf.viewer.ui.editor.view.PdfJcefPreviewController - [LOGSEVERITY_ERROR][about:blank:1]:
Uncaught ReferenceError: __messagePipe_sendMessageToBrowser is not defined
java.lang.Throwable: [LOGSEVERITY_ERROR][about:blank:1]:
Uncaught ReferenceError: __messagePipe_sendMessageToBrowser is not defined
at com.intellij.openapi.diagnostic.Logger.error(Logger.java:375)
at com.firsttimeinforever.intellij.pdf.viewer.jcef.JcefUtils.createDefaultConsoleMessageListener$lambda$0(JcefUtils.kt:104)
at com.firsttimeinforever.intellij.pdf.viewer.jcef.JcefUtils$addConsoleMessageListener$1.onConsoleMessage(JcefUtils.kt:89)
at com.intellij.ui.jcef.JBCefClient$3.lambda$onConsoleMessage$4(JBCefClient.java:342)
at com.intellij.ui.jcef.JBCefClient$HandlerSupport.handleBooleanReturnAnyOf(JBCefClient.java:779)
at com.intellij.ui.jcef.JBCefClient$3.onConsoleMessage(JBCefClient.java:341)
at jcef/com.jetbrains.cef.remote.ClientHandlersImpl.DisplayHandler_OnConsoleMessage(ClientHandlersImpl.java:354)
at jcef/com.jetbrains.cef.remote.thrift_codegen.ClientHandlers$Processor$DisplayHandler_OnConsoleMessage.getResult(ClientHandlers.java:5720)
at jcef/com.jetbrains.cef.remote.thrift_codegen.ClientHandlers$Processor$DisplayHandler_OnConsoleMessage.getResult(ClientHandlers.java:5697)
at jcef/com.jetbrains.cef.remote.thrift.ProcessFunction.process(ProcessFunction.java:38)
at jcef/com.jetbrains.cef.remote.thrift.TBaseProcessor.process(TBaseProcessor.java:40)
at jcef/com.jetbrains.cef.remote.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:257)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1090)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:614)
at jcef/com.jetbrains.cef.remote.CefServer$1.lambda$newThread$0(CefServer.java:230)
at java.base/java.lang.Thread.run(Thread.java:1474)