TestRunSessionSerializationTests4.testAllTests failed in I-build

See: https://download.eclipse.org/eclipse/downloads/drops4/I20260624-2300/testresults/html/org.eclipse.jdt.ui.tests_ep441I-unit-macosx-x86_64-java21_macosx.cocoa.x86_64_21.html

```
Launch has not terminated

java.lang.AssertionError: Launch has not terminated
at org.junit.Assert.fail(Assert.java:89)
at org.junit.Assert.assertTrue(Assert.java:42)
at org.eclipse.jdt.junit.tests.AbstractTestRunListenerTest.launchJUnit(AbstractTestRunListenerTest.java:151)
at org.eclipse.jdt.junit.tests.AbstractTestRunListenerTest.launchJUnit(AbstractTestRunListenerTest.java:137)
at org.eclipse.jdt.junit.tests.AbstractTestRunSessionSerializationTests.launchTest(AbstractTestRunSessionSerializationTests.java:88)
at org.eclipse.jdt.junit.tests.AbstractTestRunSessionSerializationTests.runExportImport(AbstractTestRunSessionSerializationTests.java:107)
at org.eclipse.jdt.junit.tests.AbstractTestRunSessionSerializationTests.runCUTest(AbstractTestRunSessionSerializationTests.java:241)
at org.eclipse.jdt.junit.tests.TestRunSessionSerializationTests4.testAllTests(TestRunSessionSerializationTests4.java:99)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
```

The test timed out, it took 30.098 sec.

The workspace log has nothing interesting: https://download.eclipse.org/eclipse/downloads/drops4/I20260624-2300/testresults/ep441I-unit-macosx-x86_64-java21_macosx.cocoa.x86_64_21/org.eclipse.jdt.ui.tests.AutomatedSuite.txt

```
!MESSAGE testAllTests STARTING
1782352500349 launch added : AllTests: org.eclipse.debug.core.Launch@20ff9c7
1782352500361 launch changed : AllTests: org.eclipse.debug.core.Launch@20ff9c7 [JUnit]

!ENTRY org.eclipse.jdt.ui.tests 1 0 2026-06-25 02:55:30.414
!MESSAGE testAllTests DONE: FAILED
```

Start with TestRunSessionSerializationTests4.testAllTests and trace the reported calls through AbstractTestRunSessionSerializationTests.launchTest and runExportImport. Reproduce the macOS Java 21 timeout, inspect the linked test results and workspace log, and consider the issue done when the test launch terminates reliably within the timeout.

Written by the indexing model from the issue text.