test(ptt): use capital 'Space' in set_binding_updates_descriptor_watch

The Windows Raw Input backend's keymap is case-sensitive; the test
passed lowercase 'space' which works for the Focused fallback on
Linux but fails on Windows where resolve_binding returns
InvalidBinding. Use the same canonical 'Space' string the bind
dialog produces in real use.

core/chanora_core/src/ptt.rs

@@ -327,7 +327,7 @@ mod tests {
         let _ = desc_rx.borrow_and_update();
         let binding = PttBinding {
             input_class: chanora_audio::PttInputClass::Keyboard,
-            platform_key: "space".to_string(),
+            platform_key: "Space".to_string(),
         };
         let new_desc = controller.set_binding(binding.clone()).await.unwrap();
         assert_eq!(new_desc.backend_id, controller.descriptor().await.backend_id);