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>

tests/core/graph.test.ts

@@ -9,10 +9,12 @@ import type { BehaviorAsset } from '../../src/core/model/Asset';
 import { createEmptyProject } from '../../src/core/model/Project';
 import { deserializeProject, serializeProject } from '../../src/core/store/serialize';
 
-function entity(name: string, x = 0): EntityHandle {
-  return { id: name, name, x, y: 0, z: 0, props: {}, parent: null };
+function entity(name: string, x = 0, assetId = `asset-${name}`): EntityHandle {
+  return { id: name, assetId, name, x, y: 0, z: 0, props: {}, parent: null };
 }
 
+const NO_POINTER = { x: 0, y: 0, inside: false, down: false, pressed: false, released: false };
+
 function context(overrides: Partial<NodeContext> = {}): NodeContext & { logs: string[]; stopped: boolean } {
   const logs: string[] = [];
   const ctx = {
@@ -25,6 +27,8 @@ function context(overrides: Partial<NodeContext> = {}): NodeContext & { logs: st
     stopped: false,
     findByName: () => null,
     isKeyDown: () => false,
+    pointer: { ...NO_POINTER },
+    hitTest: () => false,
     isTouching: () => false,
     moveAndSlide: (target: EntityHandle, dx: number, dy: number) => {
       target.x += dx;
@@ -35,6 +39,7 @@ function context(overrides: Partial<NodeContext> = {}): NodeContext & { logs: st
     spawn: () => null,
     destroy: () => {},
     stop: () => { ctx.stopped = true; },
+    restart: () => {},
     ...overrides,
   };
   return ctx;
@@ -326,7 +331,7 @@ describe('variables', () => {
 
     stack.execute(new RenameVariableCommand('mover', 'speed', 'velocity'));
     expect(behavior.variables[0]!.key).toBe('velocity');
-    expect(behavior.props).toEqual({ velocity: 0 });
+    expect(behavior.props).toEqual({ enabled: true, velocity: 0 });
     expect(object.overrides).toEqual({ velocity: 5 });
     expect(behavior.graph.nodes.find((n) => n.id === nodes.speed.node.id)!.params.variable).toBe('velocity');
     stack.undo();
@@ -373,7 +378,7 @@ describe('behavior serialization', () => {
     const loaded = deserializeProject(serializeProject(project)).assets.find((a) => a.id === 'mover') as BehaviorAsset;
     expect(loaded.variables).toEqual(behavior.variables);
     expect(loaded.graph).toEqual(behavior.graph);
-    expect(loaded.props).toEqual({ speed: 0 });
+    expect(loaded.props).toEqual({ enabled: true, speed: 0 });
 
     const raw = serializeProject(project) as { assets: { graph?: { nodes: unknown[]; edges: unknown[] } }[] };
     raw.assets[0]!.graph!.nodes.push({ id: 'zzz', type: 'DoesNotExist', x: 0, y: 0, params: {} });