fix: skip beforeunload handler in test environment

The static cleanup handler was interfering with test lifecycle,
causing the server to be killed during database migration.
Skip registration when VITEST environment variable is set.

src/server/process/WindowsProcess.ts

@@ -78,7 +78,8 @@ export class WindowsProcess implements OpenCodeProcess {
     }
 
     // Register beforeunload handler for window close cleanup
-    if (typeof window !== "undefined") {
+    // Skip in test environment to avoid interfering with test lifecycle
+    if (typeof window !== "undefined" && !process.env.VITEST) {
       window.addEventListener("beforeunload", () => {
         if (WindowsProcess.currentProcess?.pid) {
           WindowsProcess.killProcessSync(WindowsProcess.currentProcess.pid);