Re-add X-flip on image (NS-mirror) with natural order arrangement

The user wants:
- Natural order arrangement (canvasX = perp + ...): east (1102)
  on left, west (1098) on right
- X-mirrored image (NS-mirror): within each tile, the image east
  appears on the left of the tile (natural map orientation)

Combined state:
- canvasX = (perp + halfPerp + 0.5) * 256: natural order
- drawImage with negative width: X-flip (NS-mirror)
- All labels in normal orientation (no mirrorLabel)

This matches the user's description: 'die anordnung passt' (arrangement
correct) and 'der x-flip ist immer noch falsch' (image was still
mirrored, now correctly mirrored).

vendor/clouds3d.js

@@ -351,12 +351,13 @@ function drawTileAt(lng, perp, dx, dz, centerTileX, centerTileY) {
         // the corridor orientation (east tiles have their image east
         // on the left of the drawn area, west tiles on the right).
         // Labels are drawn separately in normal orientation, so the
-        // Draw image with normal orientation (no X-flip). The
+        // X-flip the image (NS-mirror). The arrangement uses the
-        // X-swap arrangement (canvasX = -perp + ...) already places
+        // natural order (canvasX = perp + ...) so east tiles are on
-        // east tiles on the right of the screen, so the X coordinates
+        // the LEFT of the screen. The image X-flip makes image east
-        // read naturally left to right when scanning the corridor.
+        // appear on the right of each east tile (the natural map
-        groundCtx.drawImage(img, canvasX, canvasY,
+        // orientation).
-            GROUND_TILE_SIZE, GROUND_TILE_SIZE);
+        groundCtx.drawImage(img, canvasX + GROUND_TILE_SIZE, canvasY,
+            -GROUND_TILE_SIZE, GROUND_TILE_SIZE);
         groundLoadedTiles[tileX + '_' + tileY] = true;
 
         // Thin border so the user can see where one tile ends and the