impl(cm): implement change_theme and change_language callbacks (#14782)

* docs: fix typos in documentation and code comments

- Fix 'seperated' -> 'separated' in remote_input.dart
- Fix 'seperators' -> 'separators' in fuse/cs.rs
- Update outdated 'OSX' -> 'macOS' in virtual display README

Signed-off-by: pallab-js <sonowalpallabjyoti@gmail.com>

* impl(cm): implement change_theme and change_language callbacks

These callbacks were previously empty TODO stubs.
Now they properly invoke the Sciter UI handlers to notify
the UI when theme or language changes occur.

Signed-off-by: pallab-js <sonowalpallabjyoti@gmail.com>

---------

Signed-off-by: pallab-js <sonowalpallabjyoti@gmail.com>

src/ui/cm.rs

@@ -52,12 +52,12 @@ impl InvokeUiCM for SciterHandler {
         self.call("newMessage", &make_args!(id, text));
     }
 
-    fn change_theme(&self, _dark: String) {
-        // TODO
+    fn change_theme(&self, dark: String) {
+        self.call("changeTheme", &make_args!(dark));
     }
 
     fn change_language(&self) {
-        // TODO
+        self.call("changeLanguage", &make_args!());
     }
 
     fn show_elevation(&self, show: bool) {