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, 22 insertions, 0 deletions

diff --git a/include/yasl/native/x11.h b/include/yasl/native/x11.h
new file mode 100644
index 0000000..c0105cb
--- /dev/null
+++ b/include/yasl/native/x11.h
@@ -0,0 +1,22 @@
+#ifndef YASL_NATIVE_X11_H
+#define YASL_NATIVE_X11_H
+
+#include "yasl/yasl.h"
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct _XDisplay Display;
+
+/* Return borrowed X11 handles (expire on display/surface destruction).
+ * Return NULL / 0 if display/surface is not an X11 object or destroyed. */
+YASL_API Display *yasl_x11_display_get_display(struct yasl_display *d);
+YASL_API uintptr_t yasl_x11_surface_get_window(struct yasl_surface *s);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* YASL_NATIVE_X11_H */