017 store backend arms di

// ASPIRATION — TODO idea pin. T8 statically-resolved DI: `! ?persist` is
// an optional resume arm on the store's contract (optional arms ruled
// 2026-07-03 @7c37406a). Installed => the write-subflow calls it per
// write (sole-write-path boundary keeps deltas coherent); not installed
// => `if(persist) | else` resolves at comptime and the arm costs nothing.
// Void side-effecting arm per the ORM-showcase grounding; the install
// SURFACE (arms on watch? on link?) is PROVISIONAL.

~import std/io
~import std/store

~std/store:create(game) { hp: 0[i64] }
! ?persist i64

~std/store:watch(game)
! persist v |> std/io:print.ln("persist {{ v:d }}")

~std/store:stored { game.hp: 4 }
~std/store:stored { game.hp: 6 }