Drop the collider and delete-node buttons from the inspector

Adding a collider now lives only in the Scene objects context menu, deleting a node on
the Delete key and the node context menu. The e2e checks that pinned the inspector button
now drive the hierarchy menu instead, including that its entry is disabled on template
content and on a placed container without raising a notice.

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

tools/e2e/06-graph.mjs

@@ -233,6 +233,8 @@ export async function graph(t) {
 
   // 13e. Delete removes the selected node together with its edge; undo brings both back.
   await select({ kind: 'node', assetId: 'mover', nodeId: newNode.id });
+  await sleep(200);
+  check('the node inspector has no delete button of its own', !(await t.has('Delete node')));
   await press('Delete');
   await sleep(150);
   const deleted = await graphCounts();