Complete the client-side draft feature on top of the shipped backend
foundation (the game_drafts store/service):
- FB: DraftRequest{game_id,json} + DraftView{json} (a draft get reuses
GameActionRequest); regenerated committed Go + TS bindings.
- Backend REST: GET/PUT /games/:id/draft, a draftDTO
(rack_order/board_tiles) mapped to game.Draft.
- Gateway: draft.get/draft.save transcode forwarding the composition
JSON verbatim (json.RawMessage both ways -- no double-encode).
- UI: debounced save of the rack order + board tiles and restore on
load (lib/draft.ts), plus #5 -- tiles may be arranged on the
opponent's turn (placement relaxed; the preview and Make-move stay
your-turn-only, so an off-turn draft is position-only).
Tests: backend handler validation, gateway pass-through round-trip, UI
draft/codec units, and a draft-restore e2e.