Add positioning strategy API and refactor menu open

Introduces PositioningStrategy abstraction for menu and UI element positioning, supporting absolute, cursor, and relative modes. Updates FFI bindings, native code, and Dart API to use positioning strategies instead of raw coordinates. Refactors menu open methods and updates example usage. Adds new exports and updates submodule and config files accordingly.

Author: lijy91

examples/menu_example/lib/main.dart

@@ -113,7 +113,7 @@ class _MenuExamplePageState extends State<MenuExamplePage>
   }
 
   void _showMenuAtPosition(Offset position) {
-    _contextMenu.open(at: position);
+    _contextMenu.open(PositioningStrategy.absolute(position));
   }
 
   void _clearHistory() {

packages/cnativeapi/example/pubspec.lock

@@ -17,6 +17,7 @@ publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 # In Windows, build-name is used as the major, minor, and patch parts
 # of the product and file versions while build-number is used as the build suffix.
 version: 1.0.0+1
+resolution: workspace
 
 environment:
   sdk: ^3.9.2

packages/cnativeapi/example/pubspec.yaml

@@ -8,22 +8,26 @@ output: "lib/src/bindings_generated.dart"
 headers:
   entry-points:
     - "src/libnativeapi/src/capi/accessibility_manager_c.h"
+    - "src/libnativeapi/src/capi/application_c.h"
     - "src/libnativeapi/src/capi/display_c.h"
     - "src/libnativeapi/src/capi/display_manager_c.h"
     - "src/libnativeapi/src/capi/geometry_c.h"
     - "src/libnativeapi/src/capi/image_c.h"
     - "src/libnativeapi/src/capi/menu_c.h"
+    - "src/libnativeapi/src/capi/positioning_strategy_c.h"
     - "src/libnativeapi/src/capi/string_utils_c.h"
     - "src/libnativeapi/src/capi/tray_icon_c.h"
     - "src/libnativeapi/src/capi/tray_manager_c.h"
 
   include-directives:
     - "src/libnativeapi/src/capi/accessibility_manager_c.h"
+    - "src/libnativeapi/src/capi/application_c.h"
     - "src/libnativeapi/src/capi/display_c.h"
     - "src/libnativeapi/src/capi/display_manager_c.h"
     - "src/libnativeapi/src/capi/geometry_c.h"
     - "src/libnativeapi/src/capi/image_c.h"
     - "src/libnativeapi/src/capi/menu_c.h"
+    - "src/libnativeapi/src/capi/positioning_strategy_c.h"
     - "src/libnativeapi/src/capi/string_utils_c.h"
     - "src/libnativeapi/src/capi/tray_icon_c.h"
     - "src/libnativeapi/src/capi/tray_manager_c.h"