:table-dataThe always-visible column Totals Row (todo 7.1) could have been modeled as a pseudo-row inside :table-data — e.g. a sentinel row number — making it addressable like any other cell (selectable, copyable, referenceable in formulas). We chose instead to compute it purely as a derived subscription that is never written into :table-data and has no row number.
A stored pseudo-row would have let future features (formula references to the total, selection/copy of totals) come for free, but it would also contaminate highest-row, cycle detection, and keyboard navigation with a fake row that isn't real data — and none of those future features are asked for by this todo item. The header row already establishes precedent for a view-only row that doesn't live in :table-data, so this keeps the totals row consistent with that existing pattern rather than introducing a new kind of row into the data model.