Navigation: theme data reference

Reading the data tables. Presence varies by page and state; this is not a requirement to populate every field.

Field	Type	Meaning	Availability
viewModel.navigation	array	Prepared navigation collection; may be empty.	When the parent is provided; check optional fields.
viewModel.navigation[].children	NavigationNode[]	Child nodes with the same label, url, isActive and children fields; recurse until empty.	Every navigation node; empty on leaf nodes.
viewModel.navigation[].isActive	boolean	True for the active category and its ancestor nodes.	Every navigation node.
viewModel.navigation[].label	string	Label value supplied for this context.	For each existing item; optional child fields depend on item type.
viewModel.navigation[].url	string	Prepared url URL; use unchanged.	For each existing item; optional child fields depend on item type.