fix(macos): prevent Bambu network plugin SIGABRT on app quit

libbambu_networking aborts inside its C++ static destructors during the
exit() teardown on macOS while its background threads are still alive.
Two quit paths reach that exit():

- App menu / Dock / logout: -[NSApplication terminate:] -> exit() bypasses
  wx OnExit()/~GUI_App. Override OSXOnWillTerminate() (the last wx hook
  before that exit()) to hard-exit via std::_Exit(0).
- Cmd+Q / File>Quit / red button: graceful close -> ~GUI_App(). A guarded
  std::_Exit(0) at the end of ~GUI_App(), after all cleanup, covers it.

macOS-only (#ifdef __APPLE__); Windows/Linux unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/slic3r/GUI/GUI_App.cpp

@@ -2215,6 +2215,16 @@ GUI_App::~GUI_App()
 
 
     BOOST_LOG_TRIVIAL(info) << __FUNCTION__<< boost::format(": exit");
+
+#ifdef __APPLE__
+    // Belt-and-suspenders for the graceful quit path (Cmd+Q / File>Quit / red button),
+    // which reaches ~GUI_App() instead of OSXOnWillTerminate(). All app cleanup has run
+    // by this point (config saved, network agent deleted, Bambu plugin shut down), so we
+    // hard-exit to ensure the C runtime's exit() never runs libbambu_networking's static
+    // destructors — they abort during teardown on macOS. This mirrors the app-menu/Dock/
+    // logout path handled in GUI_App::OSXOnWillTerminate().
+    std::_Exit(0);
+#endif /* __APPLE__ */
 }
 
 bool GUI_App::is_blocking_printing(MachineObject *obj_)
@@ -2593,6 +2603,30 @@ int GUI_App::OnExit()
     return wxApp::OnExit();
 }
 
+#ifdef __APPLE__
+// On macOS, quitting via the app menu / Dock / logout (or a system Quit AppleEvent)
+// routes through Cocoa's -[NSApplication terminate:], which calls exit() directly
+// from inside the native run loop. That bypasses wx's normal shutdown
+// (OnExit()/~GUI_App never run) and, during __cxa_finalize_ranges, runs the C++
+// static/atexit destructors of the closed-source Bambu networking plugin
+// (libbambu_networking) while its background threads are still alive. One of those
+// destructors calls std::terminate() -> abort(), producing a SIGABRT crash report
+// *after* the user has already quit (purely a teardown crash, no data at risk).
+//
+// OSXOnWillTerminate() is the last wx hook invoked before that exit(), and only
+// runs once termination has already been approved (OSXOnShouldTerminate() returned
+// no veto). We let the base class fire wxEVT_END_SESSION for any listeners, then
+// hard-exit with _Exit() so __cxa_finalize_ranges — and thus the plugin's crashing
+// destructors — never run. Nothing is persisted on this path today either, so this
+// is behavior-preserving apart from removing the cosmetic crash.
+void GUI_App::OSXOnWillTerminate()
+{
+    BOOST_LOG_TRIVIAL(info) << "GUI_App::OSXOnWillTerminate: hard-exit to avoid Bambu network plugin teardown crash";
+    wxApp::OSXOnWillTerminate();
+    std::_Exit(0);
+}
+#endif /* __APPLE__ */
+
 class wxBoostLog : public wxLog
 {
     void DoLogText(const wxString &msg) override {

src/slic3r/GUI/GUI_App.hpp

@@ -626,6 +626,10 @@ public:
     // wxWidgets override to get an event on open files.
     void            MacOpenFiles(const wxArrayString &fileNames) override;
     void            MacOpenURL(const wxString& url) override;
+    // Last wx hook before Cocoa's exit() on the app-menu/Dock/logout quit path.
+    // Hard-exits to skip the crashing static-destructor teardown of the Bambu
+    // networking plugin. See implementation in GUI_App.cpp.
+    void            OSXOnWillTerminate() override;
 #endif /* __APPLE */
 
     Sidebar&             sidebar();