Collider asset type, CollisionSystem and collision nodes

- Asset type 'collider' (box/circle) placed as child of a body object
- 'Add collider' shortcut (hierarchy context menu + inspector)
- CollisionSystem with enter/stay/exit pairs, sibling colliders excluded
- Nodes: On collision enter/stay/exit, Is touching
- Green outline in edit mode, hidden in play

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tools/e2e.mjs

@@ -541,6 +541,46 @@ try {
   o2 = JSON.parse(await objectJson('o2'));
   check('Unparent moves the object to the top level, keeping its world position', o2.parentId === '' && o2.position.x === 120 && o2.position.y === -80, JSON.stringify(o2));
 
+  // 15. Colliders. Right-click the red crate → "Add collider": a collider asset sized like the
+  //     crate (100×60) is placed as its child at the centre, selected and drawn in the overlay.
+  const redRow3 = await locate('Red crate');
+  await click(redRow3.x, redRow3.y, 'right');
+  await sleep(150);
+  await clickText('Add collider');
+  await sleep(200);
+  s = JSON.parse(await stateJson());
+  const colObj = s.selection?.kind === 'object' ? JSON.parse(await objectJson(s.selection.objectId)) : null;
+  const colAsset = colObj ? JSON.parse(await evaluate(`JSON.stringify(__gm.state.project.assets.find(a => a.id === '${colObj.assetId}'))`)) : null;
+  check('Add collider creates a collider child sized like the sprite', colObj?.parentId === 'o1' && colAsset?.type === 'collider' && colAsset.props.width === 100 && colAsset.props.height === 60, JSON.stringify({ colObj, colAsset }));
+  check('collider is drawn in the overlay layer', colObj && (await evaluate(`__gm.layerOf('${colObj.id}')`)) === 'overlay');
+  check('collider inspector shows the shape menu', Boolean(await evaluate(`__gm.locate('Box ▾')`)));
+  await shot('21-collider');
+
+  // 15a. Give the blue crate the same collider, wire "On collision enter → Log(other)" into the
+  //      Mover (owner = red crate) and play with the crates overlapping: the log names the blue
+  //      crate exactly once (enter, not stay), and colliders are not rendered in play mode.
+  await evaluate(`(() => {
+    const scene = __gm.state.activeScene;
+    scene.objects.push({ id: 'oc2', assetId: '${colAsset.id}', name: '', position: { x: 0, y: 0, z: 0 }, overrides: {}, parentId: 'o2' });
+    const mover = __gm.state.project.assets.find(a => a.id === 'mover');
+    mover.graph.nodes.push({ id: 'n-hit', type: 'OnCollisionEnter', x: 0, y: 600, params: {} }, { id: 'n-hitlog', type: 'Log', x: 340, y: 600, params: {} });
+    mover.graph.edges.push(
+      { id: 'e-hit1', from: { node: 'n-hit', port: 'exec' }, to: { node: 'n-hitlog', port: 'exec' } },
+      { id: 'e-hit2', from: { node: 'n-hit', port: 'other' }, to: { node: 'n-hitlog', port: 'message' } });
+    scene.objects.find(o => o.id === 'o2').position = { x: -100, y: 0, z: 0 }; // 50 from the red crate → 100-wide boxes overlap
+    __gm.state.select(null);
+    __gm.state.preview();
+  })()`);
+  await keyPress('Enter', 'Enter', { modifiers: 2, windowsVirtualKeyCode: 13 });
+  await sleep(500);
+  const collisionWorld = JSON.parse(await evaluate('JSON.stringify(__gm.world())'));
+  check('On collision enter fired once with the other body', collisionWorld && collisionWorld.log.filter((l) => l === 'Blue crate').length === 1, JSON.stringify(collisionWorld?.log));
+  const spriteCount = await evaluate(`__gm.state.activeScene.objects.filter(o => __gm.state.project.assets.find(a => a.id === o.assetId)?.type === 'sprite').length`);
+  info = await evaluate('JSON.stringify(__gm.viewportInfo())');
+  check('colliders are not rendered in play mode', JSON.parse(info).visibleItems === spriteCount, `${info} sprites=${spriteCount}`);
+  await keyPress('Escape', 'Escape', { windowsVirtualKeyCode: 27 });
+  await sleep(200);
+
   check('no exceptions during run', !consoleLog.some((l) => l.startsWith('EXCEPTION')), consoleLog.filter((l) => l.startsWith('EXCEPTION')).slice(0, 3).join(' | '));
   ws.close();
 } catch (error) {