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>

tools/projects.mjs

@@ -0,0 +1,58 @@
+#!/usr/bin/env node
+/**
+ * Which project each tool writes to, and the guard that keeps the checks away from the
+ * playground.
+ *
+ *   demo       the project served at ?project=… in the browser. It is the user's playground;
+ *              only tools/seed-demo.mjs may overwrite it, and only when asked.
+ *   fixture    rewritten by every e2e run. tools/e2e.mjs mutates it heavily.
+ *   demoCheck  a throwaway copy of the demo scene for tools/smoke-demo.mjs.
+ *   jumpRun    the example game (tools/seed-jumprun.mjs, checked by tools/smoke-jumprun.mjs).
+ *
+ * All ids exist on the server (created via POST ?r=projects); PUT does not create projects.
+ */
+export const PROJECTS = {
+  demo: '649188c15414',
+  fixture: '3caa9b6a0c92',
+  demoCheck: 'aaf5e962ef9c',
+  jumpRun: '3d271f3bb58b',
+};
+
+export const DEFAULT_BASE_URL = 'https://nockal.com/game-maker/';
+
+/**
+ * Reads `[projectId] [baseUrl]` from argv, falling back to `defaultId`. Unless `allowDemo` is
+ * set, targeting the demo project aborts: a destructive run must never hit the playground.
+ */
+export function cliArgs(script, defaultId, { allowDemo = false } = {}) {
+  const projectId = process.argv[2] ?? defaultId;
+  const baseUrl = process.argv[3] ?? DEFAULT_BASE_URL;
+  if (!projectId) {
+    console.error(`usage: node tools/${script} <projectId> [baseUrl]`);
+    process.exit(2);
+  }
+  if (!allowDemo && projectId === PROJECTS.demo) {
+    console.error(`refusing to run ${script} against the demo project (${PROJECTS.demo}) – it is the playground.`);
+    process.exit(2);
+  }
+  return { projectId, baseUrl };
+}
+
+/** Overwrites a project, keeping the name it already has on the server. */
+export async function writeProject(projectId, baseUrl, project) {
+  const url = `${baseUrl}api/index.php?r=projects/${projectId}`;
+  const current = await fetch(url);
+  if (!current.ok) {
+    console.error(`GET failed: ${current.status} – create the project first (POST ?r=projects)`);
+    process.exit(1);
+  }
+  const doc = await current.json();
+  const body = { revision: doc.revision, project: { ...project, id: projectId, name: doc.name ?? project.name } };
+  const res = await fetch(url, { method: 'PUT', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(body) });
+  const result = await res.json();
+  if (!res.ok) {
+    console.error('PUT failed', res.status, result);
+    process.exit(1);
+  }
+  console.log(`seeded ${projectId} (${body.project.name}) → revision ${result.revision}`);
+}