OptionalinitialThe studio tracker's initial anchor (see Command.FocusActivation's constructor). Typically a
Command.DefaultAnchorProvider provider (a function) that returns the loaded grid's
would-focus pane element — invoked pre-reveal so the toolbar paints enabled without the grid stealing
real focus, AND re-invoked when a resize destroys the anchored pane (the destruction fallback). A
one-shot Promise/value is also accepted (seeds once, no recall). Captured at mount; real focus
advances the anchor thereafter.
Establishes the shared command root (registry +
appscope + the one studio focus tracker + the one studio resolver with its synthetic key seam) for one mounted app. The per-workbook (WorkbookElement) and per-sheet (SheetCommandProvider) providerscreateChildtheir instance scopes off the ambient scope this publishes.Provide-or-inherit (the SurfaceStateProvider idiom): if an ancestor already established a root, an ambient command scope exists — so this is a pass-through, and a studio establishes ONE root that both its chrome (toolbar / formula bar) and its
WorkbookElement(s) share, while a bare chromelessWorkbookElementthat finds none establishes its own. TwoWorkbookElements under one studio therefore share one registry +rootand each owns a distinctworkbookinstance — the substrate for the pending-workbook swap.It owns only instance-independent infrastructure. The catalog (chrome) is seeded by each feature provider into the shared registry (idempotent by contributor identity), and all model-closured behavior lives on the per-workbook / per-sheet instances below.