Keep Glass attached through target-worker shutdown

Early Platform.exit detached JavaFX while queued macOS activation callbacks still called Java. Close the owned example before terminating its JVM, make shutdown idempotent, and reject late preview work. Add real startup-cancellation regressions and native crash-report checks.

scripts/check-ide-host.py

@@ -12,6 +12,7 @@ import subprocess
 import sys
 import time
 import zipfile
+from native_crashes import NativeCrashGuard, descendant_workers, await_worker_exit
 
 ROOT = Path(__file__).resolve().parent.parent
 p = argparse.ArgumentParser(description=__doc__)
@@ -22,6 +23,7 @@ args = p.parse_args()
 output = ROOT / "target/ide-workflow"
 output.mkdir(parents=True, exist_ok=True)
 for mode in ("classpath", "modulepath"):
+    crashes = NativeCrashGuard(ROOT)
     launch = subprocess.run([sys.executable, ROOT / "scripts/run-fixture-host.py", "intellij",
         "--check", "--mode", mode, "--java-home", args.java_home,
         "--target-java-home", args.target_java_home, "--idea-home", args.idea_home],
@@ -58,9 +60,12 @@ for mode in ("classpath", "modulepath"):
                  "result": (base / "SUCCESS.txt").read_text()}
         (output / (mode + ".json")).write_text(json.dumps(proof, indent=2) + "\n")
         shutil.copyfile(base / "intellij.png", output / (mode + ".png"))
-        print("PASS registered IntelliJ " + mode + " editor and exclusive JavaFX 26 natives", flush=True)
     finally:
+        workers = descendant_workers(pid)
         try:
             os.kill(pid, signal.SIGTERM)
         except ProcessLookupError:
             pass
+        await_worker_exit(workers)
+        crashes.check()
+    print("PASS registered IntelliJ " + mode + " editor, exclusive JavaFX 26 natives and worker shutdown", flush=True)