update widgets, add copy paste buffer

src/platform/platform.h

@@ -79,3 +79,9 @@ int32_t         platform_poll_menu_command(PlatformWindow *window);
 
 // Returns accumulated input events since last call, then clears the buffer.
 PlatformInputEvents platform_get_input_events(PlatformWindow *window);
+
+// 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.
+void        platform_clipboard_set(const char *text);
+const char *platform_clipboard_get();