Enabled switch, text assets, mouse input and the jump-and-run example game

Engine additions that the example game needed:
- `enabled` as a shared property of every placeable asset (default on, an
  override on the scene object). A switched-off object is not drawn, does not
  collide and its behavior does not run - and neither does anything parented
  below it. Disabled objects are now hidden in the scene view as well, so the
  editor shows what the game shows; they stay in the hierarchy panel, which is
  where they are selected and switched back on.
- Asset type `text` (text, fontSize, color, align), rendered in scene and game.
- Pointer input in the game view: `On click`, `Mouse position`, `Mouse button`,
  `Is hovered`, hit-tested against colliders, else sprite/text footprints.
- New nodes: Set/Is enabled, Set text, Is asset, Name of, Equals, To text,
  Join text, Floor/Ceil/Round, Modulo, Random, Time, Restart game.

Tooling: shared CDP harness (tools/harness.mjs), central project registry with
a guard that keeps destructive scripts off the playground (tools/projects.mjs),
plus smoke suites for the demo scene and the jump-and-run game.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/model/Asset.ts

@@ -20,6 +20,14 @@ export interface CameraAsset extends AssetBase {
   type: 'camera';
 }
 
+/**
+ * A line of text drawn in the scene (titles, HUD readouts, buttons). Its content is the
+ * ordinary property `text`, so behaviors change it with `Set text` (or `Set property`).
+ */
+export interface TextAsset extends AssetBase {
+  type: 'text';
+}
+
 /** A scene is an asset that additionally owns the objects placed into it. */
 export interface SceneAsset extends AssetBase {
   type: 'scene';
@@ -57,7 +65,7 @@ export interface ContainerAsset extends AssetBase {
   objects: SceneObject[];
 }
 
-export type Asset = SpriteAsset | CameraAsset | SceneAsset | BehaviorAsset | ColliderAsset | ContainerAsset;
+export type Asset = SpriteAsset | CameraAsset | TextAsset | SceneAsset | BehaviorAsset | ColliderAsset | ContainerAsset;
 
 export function isSceneAsset(asset: Asset): asset is SceneAsset {
   return asset.type === 'scene';