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.
ScriptComponent stores only a script name string (POD, serializable);
instances are reconciled by ScriptRuntime each frame (PhysicsWorld
pattern): orphan/rename cleanup with OnDestroy, per-name instantiation
from a file-level self-registering registry (ENGINE_REGISTER_SCRIPT),
OnCreate on bind, OnUpdate after physics step on scaled dt. Engine
framerate loop only sees the base interface, so future Lua/C# behaviors
plug in as foreign ScriptBehavior implementations with zero engine
changes. Ships a Spinner sample script and Inspector script picker.