feat: add type-safe native platform headers and portable drag support

- Add include/yasl/native/{wayland,cocoa,x11}.h with type-safe handle accessors.
- Unify drag-and-drop and window carry support across Wayland, X11, and Cocoa.
- Preserve full ABI compatibility for capability flags.
- Install native headers conditionally based on enabled backend.
- Include missing tablet example and backend test suites.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/wayland/api.h b/src/wayland/api.h
index 87e896d..e68aca7 100644
--- a/src/wayland/api.h
+++ b/src/wayland/api.h
@@ -2,6 +2,7 @@
 #define YASL_WAYLAND_API_H
 
 #include "common/backend.h"
+#include "yasl/native/wayland.h"
 
 struct wayland_display;
 struct wayland_surface;