Refactor: merge duplicated rules, split the largest files by topic (t21)

- One helper each for wall and mold refunds, tube edges and lanes, pipe text, piece dimensions,
  font lookup, reach circles and surface averaging.
- previews, smooth, notebook, materials, worldgen and selection split into topic files
  (preview-drill, preview-selection, smooth-shaders, notebook-market, notebook-blueprints,
  material-tables, worldgen-helpers, selection-pickers, selection-panels).
- Every suite's output identical apart from timings; seeds make the same worlds.

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

src/ui/actions.js

@@ -124,7 +124,7 @@ function primaryPress(shift) {
     const P = piece();
     if (P.kind === 'block') { GAME.drag = aimBlock(); }
     else {
-      const bw = P.kind === 'mold' ? MOLDS[P.mold].bw : P.bw, bh = P.kind === 'mold' ? MOLDS[P.mold].bh : P.bh;
+      const { bw, bh } = pieceSize(P);
       const { bx, by } = stampOrigin(bw, bh);
       if (!inReach(bx * BS + bw * BS / 2, by * BS + bh * BS / 2)) { setStatus('Out of reach.'); playSfx('error'); return; }
       const place = () => P.kind === 'mold' ? placeMoldAt(P.mold, bx, by, GAME.wallMat) : placeMachineAt(P.id, GAME.pieceDir[P.id] || 0, bx, by);