test: print all threads when a test times out

The rare CI hang in SelectedStationMessageUiVisualRenderingTest blocks on a
monitor in SnapshotStateObserver.observeReads (line 643 is the monitorenter
of observedScopeMapsLock in Compose 1.8.2). The timed-out thread's stack
shows where it waits but not which thread holds the lock. With the thread
dump enabled, JUnit prints every thread to the test's standard output, which
ends up in the XML report of the test-results artifact.

Claude-Session: https://claude.ai/code/session_01FJBfPYm6rCH4zD6T7bcC7Y

build.gradle.kts

@@ -151,6 +151,13 @@ subprojects {
          */
         systemProperty("junit.jupiter.execution.timeout.default", "2m")
         systemProperty("junit.jupiter.execution.timeout.thread.mode.default", "SEPARATE_THREAD")
+        /*
+         * The timed-out thread's stack shows where a test waits, not who it waits for: the
+         * rare CI hang in SelectedStationMessageUiVisualRenderingTest blocks on a monitor
+         * that another thread holds. On a timeout JUnit prints all threads to the test's
+         * standard output, which lands in its XML report (the test-results artifact).
+         */
+        systemProperty("junit.jupiter.execution.timeout.threaddump.enabled", "true")
         // The default short format prints only the first frame of each cause, which for a
         // timed-out test is the line it hung in but not the call that blocked there.
         testLogging {