set layout size draggble

src/platform/platform.h

@@ -90,6 +90,15 @@ int32_t         platform_poll_menu_command(PlatformWindow *window);
 // Returns accumulated input since last call (keyboard events + polled mouse state), then clears the buffer.
 PlatformInput platform_get_input(PlatformWindow *window);
 
+// Cursor shapes for resize handles
+enum PlatformCursor {
+    PLATFORM_CURSOR_ARROW   = 0,
+    PLATFORM_CURSOR_SIZE_WE = 1,  // horizontal resize
+    PLATFORM_CURSOR_SIZE_NS = 2,  // vertical resize
+};
+
+void platform_set_cursor(PlatformCursor cursor);
+
 // Clipboard operations (null-terminated UTF-8 strings).
 // platform_clipboard_set copies text to the system clipboard.
 // platform_clipboard_get returns a pointer to a static buffer (valid until next call), or nullptr.