Screw conveyors join across the corner to diagonals (t62)

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

src/sim/conveyors.js

@@ -176,6 +176,20 @@ function screwIntake(i, p, dx, dy) {
   }
 }
 
+// A straight mouth can feed a diagonal tail one block across the corner.
+function straightScrewNext(i, p) {
+  const dx = SCREW_DX[p], dy = SCREW_DY[p], x = i % W, y = (i / W) | 0;
+  const xx = x + dx, yy = y + dy, next = i + dx + dy * W;
+  if (xx < 0 || yy < 0 || xx >= W || yy >= H) return -1;
+  if (((xx >> 2) === (x >> 2) && (yy >> 2) === (y >> 2)) || part[next] || blockP[(yy >> 2) * BW + (xx >> 2)]) return next;
+  for (let side = -1; side <= 1; side += 2) {
+    const nx = xx + (dx ? 0 : side * BS), ny = yy + (dy ? 0 : side * BS);
+    if (nx < 0 || ny < 0 || nx >= W || ny >= H) continue;
+    const j = ny * W + nx, q = part[j];
+    if (SCREW_DX[q] === (dx || side) && SCREW_DY[q] === (dy || side)) return j;
+  }
+  return next;
+}
 // Four lanes cross a block in four beats; the casing carries every lane across the corner.
 // Prefer the next diagonal block, then either straight join, then the open head.
 function diagonalScrewNext(i, p) {