Remove the Refiner and Stone cutter; old saves refund them on load (t4)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/sim/pieces.js

@@ -65,12 +65,8 @@ const PIECES = [
     desc: 'Makes power when liquid falls through it. More flow, more power.' },
   { id: 'fan', name: 'Fan', kind: 'machine', bw: 1, bh: 1, cost: [[CASH, 60]], dirs: ['right', 'down', 'left', 'up'],
     desc: 'Blows gas and forces air into fires, making them far hotter: its stream reaches 28 grains and passes through grates but not walls. Its copper body melts at 1085°C, so keep it outside the furnace, a block clear of the wall, blowing in through a grate. Press F to switch it on or off.' },
-  { id: 'cutter', hidden: true, name: 'Stone cutter', kind: 'machine', bw: 2, bh: 2, cost: [[CASH, 90]],
-    desc: 'A saw under a hopper. Stone rubble dropped in is cut into stone bricks, one from every 8 grains, which drop out underneath. Builders buy stone bricks, and they make neat cut stone walls that stand more heat than rough stone. Anything else falls straight through.' },
   { id: 'silo', name: 'Silo', kind: 'machine', bw: 3, bh: 6, cost: [[CASH, 180]],
     desc: 'A steel bin on legs for one loose material: up to 4,000 grains go in through the hatch in its roof (drop them in from a belt or tube). Its gauge shows how full it is. Press F to open the gate in its cone and let it out underneath, about 60 grains a second; F again shuts it. The first material in decides what it holds until it is empty.' },
-  { id: 'refiner', hidden: true, name: 'Refiner', kind: 'machine', bw: 3, bh: 3, cost: [[CASH, 120]],
-    desc: 'A crushing sieve. Drop stone, granite or basalt rubble, gravel, sand or dirt into its hopper: it grinds each grain, keeps the odd grain of ore it finds (clay, from dirt) and lets about half as much fine sand out of the chute underneath. Ore and anything else it cannot grind falls straight through. Keep the space under the chute clear, or a belt running under it.' },
   { id: 'engine', name: 'Steam engine', kind: 'machine', bw: 3, bh: 2, cost: [[BARCU, 10]], dirs: ['exhaust right', 'exhaust left'], hidden: POWER_FREE,
     desc: 'Steam rising into the intake slots on its underside drives it. Condensate drips out the exhaust side.' },
   { id: 'dock', name: 'Trade dock', kind: 'machine', bw: 6, bh: 4, cost: [], hidden: true, fixed: true,