Sloped belts hold their load with moving cleats (t42); sloped filters are downhill shaking screens (t43)

The magic grip is gone: cleats every 8 face cells, 6 grains tall, carry
pockets uphill (about 71 grains/s against 90 flat) and overflow rolls
back. Sloped filters always run downhill; grains travel by gravity and
a shake, and sorting stays exact. Drawing needs another pass.

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

src/manifest.json

@@ -20,6 +20,7 @@
     "sim/pipes.js",
     "sim/machine-tick.js",
     "sim/conveyors.js",
+    "sim/slope-conveyors.js",
     "sim/blocks.js",
     "sim/molds.js",
     "sim/items.js",