Function ensureDefaultLayoutTabs

src/browser/utils/rightSidebarLayout.ts:110–123

* Ensure every `inDefaultLayout: true` tab from the registry is present in * `state`. Missing tabs are appended to the first tabset (the natural * upper-left landing spot) without changing the active tab. Already-present * tabs are left where the user moved them.

(state: RightSidebarLayoutState)

 * tabs are left where the user moved them.
 */
function ensureDefaultLayoutTabs(state: RightSidebarLayoutState): RightSidebarLayoutState {
  const required = getDefaultLayoutTabIds();
  if (required.length === 0) return state;

  const present = new Set<TabType>(collectAllTabs(state.root));
  const missing: TabType[] = required.filter((tab) => !present.has(tab));
  if (missing.length === 0) return state;

  const firstTabsetId = findFirstTabsetId(state.root);
  if (!firstTabsetId) return state;

  const root = appendTabsToTabset(state.root, firstTabsetId, missing);
  return root === state.root ? state : { ...state, root };
}

/** Append tabs to the named tabset, returning a new tree (or the original if unchanged). */
function appendTabsToTabset(