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, 19 insertions, 0 deletions

diff --git a/tests/test_api.cpp b/tests/test_api.cpp
index 70c4ff7..9fb8525 100644
--- a/tests/test_api.cpp
+++ b/tests/test_api.cpp
@@ -1,4 +1,10 @@
 #include "yasl/native.h"
+#if YASL_HAS_WAYLAND
+#include "yasl/native/wayland.h"
+#endif
+#if YASL_HAS_X11
+#include "yasl/native/x11.h"
+#endif
 #include "yasl/loop.h"
 #include <yasl/timing.h>
 #include <yasl/yasl.h>
@@ -23,5 +29,18 @@ int main()
 
     yasl_input_event event{};
     assert(!yasl_surface_input_poll(nullptr, &event));
+    assert(!yasl_display_drag_start(nullptr, nullptr, nullptr, nullptr, nullptr));
+    assert(!yasl_surface_drag_carry(nullptr, {0, 0}));
+
+#if YASL_HAS_WAYLAND
+    assert(!yasl_wayland_display_get_wl_display(nullptr));
+    assert(!yasl_wayland_surface_get_wl_surface(nullptr));
+#endif
+
+#if YASL_HAS_X11
+    assert(!yasl_x11_display_get_display(nullptr));
+    assert(!yasl_x11_surface_get_window(nullptr));
+#endif
+
     return 0;
 }