Mobile TableView: per-property RankableStack + reactor avatars + sortable headers

Deferred from Phase 3 mobile redesign (T23, C7 correction). TableView ships with value-only cells (plain text from propertyValues). The following are not yet built:

1. Per-property RankableStack: each property cell should render a RankableStack showing reactions for that property key (not just the _option key).
2. Reactor avatars: show participant avatars in the stack (matching web IdentityCell pattern).
3. Sortable headers: tapping a column header should sort the table by that property value.

Reference: apps/mobile/components/views/TableView.tsx Web equivalent: apps/web/components/options/IdentityCell.tsx (propertyKey reactions)