fix: remove app event filters on view destruction (crash on plugin reload)

The acme, palette, radial, and switch views each call
qApp->installEventFilter(this) but never removed it. QObject only auto-removes
event filters installed *on itself*, not filters it installed on *another*
object (here qApp). So when a plugin .so is unloaded/reloaded — e.g. reinstalling
the plugin — the view is destroyed while qApp still holds a dangling pointer to
it in its filter list, and the next dispatched event calls into freed memory:

  QCoreApplicationPrivate::sendThroughApplicationEventFilters -> SIGSEGV

Add qApp->removeEventFilter(this) to each view destructor (giving AcmeView a real
dtor body instead of =default). 18/18 ctest green.

src/acme/acmeplugin.cpp

@@ -193,7 +193,13 @@ AcmeView::AcmeView(AcmePlugin *plugin, KTextEditor::MainWindow *mainWindow)
     qApp->installEventFilter(this);
 }
 
-AcmeView::~AcmeView() = default;
+AcmeView::~AcmeView()
+{
+    // Remove the application event filter we installed on qApp; QObject only
+    // auto-removes filters installed on itself. Without this, a plugin
+    // unload/reload leaves qApp with a dangling filter pointer -> crash.
+    qApp->removeEventFilter(this);
+}
 
 QAction *AcmeView::findActionByName(const QString &nameOrText) const
 {

src/palette/paletteplugin.cpp

@@ -124,6 +124,10 @@ PaletteView::PaletteView(PalettePlugin *plugin, KTextEditor::MainWindow *mainWin
 
 PaletteView::~PaletteView()
 {
+    // We installed this on qApp; QObject only auto-removes filters installed on
+    // itself, so remove ours explicitly. Otherwise, on plugin unload/reload
+    // qApp keeps a dangling filter pointer and the next event crashes.
+    qApp->removeEventFilter(this);
     delete m_palette;
 }
 

src/radial/radialplugin.cpp

@@ -83,6 +83,10 @@ RadialView::RadialView(RadialPlugin *plugin, KTextEditor::MainWindow *mainWindow
 
 RadialView::~RadialView()
 {
+    // Remove the application event filter we installed on qApp; QObject only
+    // auto-removes filters installed on itself. Without this, a plugin
+    // unload/reload leaves qApp with a dangling filter pointer -> crash.
+    qApp->removeEventFilter(this);
     delete m_radial;
 }
 

src/switch/switchplugin.cpp

@@ -143,6 +143,10 @@ SwitchView::SwitchView(SwitchPlugin *plugin, KTextEditor::MainWindow *mainWindow
 
 SwitchView::~SwitchView()
 {
+    // Remove the application event filter we installed on qApp; QObject only
+    // auto-removes filters installed on itself. Without this, a plugin
+    // unload/reload leaves qApp with a dangling filter pointer -> crash.
+    qApp->removeEventFilter(this);
     delete m_filePalette;
     delete m_symbolPalette;
 }