Canonical ids (the unified `Key ?? structural-path` scheme) of every node carrying at least one event binding. The same scheme as `EventBindings` and `Bounds`, so a recovered id is a direct membership/lookup key. Populated by `renderTree` and `render` (and the retained path); read by `nearestAuthored`.

Evaluated absolute bounds of every laid-out control, keyed by `ControlId` (one entry per laid-out control instance). Populated by `Control.renderTree` from the computed `LayoutResult`; the preview `Control.render` leaves it empty. A host joins this with `EventBindings` (also keyed by `ControlId`) for hit-testing.