fix: prevent crash on __weak NSWindow ref from JNI thread during disposal

[kdroidFilter]

Summary

• nativeRemoveMenuBarMonitor and nativeResetTitleBar were creating __weak NSWindow* references on the AWT-EventQueue Java thread via objc_initWeak, which accesses the object's memory — crashing with EXC_BAD_ACCESS if the NSWindow was already deallocated on the main thread
• Replaced with raw pointer capture + dispatch_async to main thread, validating the window is still alive via [NSApp windows] pointer comparison before accessing it
• This is a follow-up to fix: prevent crash on NSWindow cleanup during fullscreen #97 which fixed a similar cleanup crash during fullscreen transitions

Test plan

• Launch the app and close the window rapidly — no crash
• Enter/exit fullscreen repeatedly while closing — no crash
• Verify menu bar monitor installs/removes correctly during fullscreen on non-notch displays
• Verify title bar reset works correctly on window close