saveState

Snapshot for process-death restoration.

Returned shape is opaque to callers — the binding factories (ViewModel / rememberSaveable) are responsible for routing it to the correct platform storage.

The snapshot is intentionally minimal: only frame primitives and per-item dynamic state (isEnabled / isSelected / isVisible), keyed by the item's stable actionId. The item list itself (icons, content descriptions, structure, click handlers) is re-supplied by the binder on restore — sidestepping the lambda-persistence problem in ToolbarIcon.Composed and matching ADR-Toolbar-4. Saving uses actionId rather than id so snapshots survive R.id churn across SDK versions.