Sidewall belt and screen drawing, cheaper cleat checks (t42, t43)

Far sidewall drawn behind the load with cleat ribs at their physics
positions; sloped screens get a tinted mesh between rails and shake only
when loaded. Powder skips cleat checks outside chunks that have cleats,
and empty slopes let their chunks sleep. Record the screw conveyor and
stall/carry-depth decisions.

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

docs/DESIGN.md

@@ -411,6 +411,12 @@ above, including:
   shake; none climbs a 45° slope. So filters are flat or downhill
   only; to sort while lifting, run a sloped belt up, then a filter. Not built yet.
 
+- **Conveyor drawing and sleep follow-up (t42/t43, 2026-10-26).** The owner wants visible
+  rubber ribs on the actual cleat raster, filled corrugated far walls behind the load, and
+  smooth continuous mesh with rails for inclined screens. Walls stop at the slope ends;
+  only loaded screens shake. Empty moving cleats must let chunks sleep. Keep pocket transport,
+  uphill throughput near 71 grains/s and exact sorting unchanged.
+
 - **Sidewall belts with moving cleats (t42, 2026-10-26).** To replace the old full-column
   grip, use moving barrier lines rather than material cells: the barrier mask blocks normal
   powder movement without overwriting grains, terrain or parts. Cleats stand perpendicular
@@ -432,6 +438,17 @@ above, including:
   Both looks use a sturdy mesh frame with a small tick-based shake only while loaded;
   idle mesh has no running belt animation. No old uphill-save migration was added.
 
+- **Screw conveyors stay, in every direction (2026-10-26).** The owner asked whether screw
+  conveyors are still needed now that belts climb 45°, whether they're realistic, and what a
+  downward screw is for. Kept as they are: real plants use both (screws for steep, vertical and
+  enclosed runs; belts for long, cheap, high-volume ones), and a downward screw is the same
+  machine turning the other way, useful for letting material down at a steady rate.
+- **Stalls are the player's to fix, but visible; belts carry a realistic depth (t45,
+  2026-10-26).** An overloaded belt line jammed against a screw conveyor above it. The owner
+  agreed that's realistic and stays the player's problem, but wants a warning on the stalled
+  belt and the animation stopped on everything affected, and belts limited to a realistic
+  load depth instead of carrying 96-grain stacks. Not built yet.
+
 ## Ideas not built yet
 
 - **Concrete**, as a stronger wall material from rubble.