feat(app): WASDMove script (WASD camera-relative movement)

ScriptBehavior gains App() host access (Application injected via
ScriptRuntime), TryGet<T> and EntityBits for physics facade addressing.
WASDMove maps WASD to the editor camera's horizontal heading (UE
gameplay convention): dynamic bodies go through the physics velocity
facade preserving the vertical component (zeroing Y would cancel
gravity mid-fall), bodiless entities translate their transform directly.
Editor-mode key conflict is naturally avoided: RMB-held flight consumes
WASD, release hands keys to the script.

Engine/src/Scripting/ScriptRuntime.cpp

@@ -10,6 +10,12 @@
 namespace Engine {
     namespace Scripting {
 
+        // 宿主门面访问器：Application 完整类型只在脚本 cpp 里需要，
+        // 这里仅回引成员（避免引擎头循环依赖）
+        Application& ScriptBehavior::App() const {
+            return *m_App;
+        }
+
         void ScriptRuntime::Update(f32 dt) {
             Sync();
 
@@ -61,7 +67,7 @@ namespace Engine {
                                 sc.scriptName, bits);
                     continue;
                 }
-                behavior->Bind(m_Scene, e);
+                behavior->Bind(m_Scene, e, m_App);
 
                 ScriptInstance inst;
                 inst.behavior = std::move(behavior);