Editor offset, global On click, Coin container in the jump-and-run seed

- SceneObject.editorOffset (x/y): shifts only where an object is drawn in
  the Scene tab, cascades to children, undo-able with a reset action.
  Never written into container templates.
- On click without an owner now fires for any click inside the camera
  frame instead of hit-testing the (editor-only) behavior symbol.
- seed-jumprun: coins are a "Coin" container (sprite + trigger), nested
  containers are expanded recursively, Destroy targets the coin's parent,
  and the clock uses a Ceil node instead of ToText.

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

src/core/store/serialize.ts

@@ -77,11 +77,14 @@ function normalizeObjects(raw: unknown, schemas: Map<string, PropertySchema>): S
     const schema = schemas.get(o.assetId);
     if (!schema || schema === schemaFor('scene')) continue; // dangling reference or illegal scene-in-scene
     const p = asRecord(o.position);
+    const offset = asRecord(o.editorOffset);
     objects.push({
       id: o.id,
       assetId: o.assetId,
       name: typeof o.name === 'string' ? o.name : '',
       position: { x: toNumber(p.x), y: toNumber(p.y), z: toNumber(p.z) },
+      // Editor-only view shift; absent in documents written before it existed.
+      editorOffset: { x: toNumber(offset.x), y: toNumber(offset.y) },
       overrides: normalizeBag(o.overrides, schema, true),
       // `ownerId` is the pre-hierarchy name of the same link (documents saved before parenting).
       parentId: typeof o.parentId === 'string' ? o.parentId : typeof o.ownerId === 'string' ? o.ownerId : '',