fix(snic): normalize canvas_size to c(width, height) convention

SNIC returned canvas_size as c(height, width) while build_svg_header()
expects c(width, height), causing the SVG viewBox to swap dimensions
and the image to appear cropped.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pjt222

R/image_fill_rendering.R

@@ -93,15 +93,9 @@ render_image_filled_pieces <- function(pieces, image_data_uri, canvas_size,
     colors <- rep(colors, length(pieces))
   }
 
-  # Image dimensions in canvas mm units
+  # Image dimensions in canvas mm units — canvas_size is always c(width, height)
   img_w <- canvas_size[1]  # width
   img_h <- canvas_size[2]  # height
-  # If canvas_size is c(height, width), swap
-  if (!is.null(image_width) && !is.null(image_height)) {
-    # Use actual canvas_size values (already in mm from generate_puzzle)
-    img_w <- canvas_size[2]  # width is second element
-    img_h <- canvas_size[1]  # height is first element
-  }
 
   sapply(seq_along(pieces), function(i) {
     piece <- pieces[[i]]

R/snic_puzzle.R

@@ -222,7 +222,7 @@ generate_snic_pieces_internal <- function(seed, grid, size, image_path,
 
   list(
     pieces = pieces,
-    canvas_size = size,
+    canvas_size = c(size[2], size[1]),  # Convert from c(height, width) to c(width, height)
     canvas_offset = c(0, 0),
     type = "snic",
     parameters = parameters,