Sloped walls with a flat 45° face, and diagonal wall lines (t36)

- New Sloped wall piece: a half-block triangle in any wall material, at half a wall's cost.
  Dragging walls or slopes at about 45° lays a diagonal line; the drag picks the slope's
  orientation and T flips or turns it.
- Each slope fills one cell past its corner, so a diagonal run is sealed against grains and water.
- New test/t_slopes.js: a slope funnel passes 400/400 sand (square steps 379/400).

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

src/ui/info.js

@@ -124,7 +124,7 @@ function hoverInfo(ax, ay) {
     if (b === BP_PUMP) t2.push(v & 4 ? 'off · press F' : 'on · F turns it off');
     if (b === BP_OUTLET) t2.push(v & 4 ? 'closed · press F' : 'open · F closes it');
   }
-  else if (b === BP_WALL && PH[m] === PH_SOLID && !(flags[i] & F_NAT)) t1 = `${MD[m].name} block`;
+  else if (isWall(b) && PH[m] === PH_SOLID && !(flags[i] & F_NAT)) t1 = `${MD[m].name} ${isSlope(b) ? 'sloped wall' : 'block'}`;
   const n = nets[netId[i]];
   if (n && isPow[i] && !POWER_FREE) t2.push(`network ${n.supply.toFixed(1)} supply / ${n.demand.toFixed(1)} demand`);
   if (player.lens && !bar) t2.push(fmtT(temp[i]));