CVE-2026-80101: size the XWD 1-bit scanline buffers on the number of bytes
the decode loops actually read, ceil(width / 8), instead of trusting
l_bytes_per_line alone, and zero-fill them; the upstream guard is
re-authored because its own arithmetic is inoperative
CVE-2026-82343: reject PSD files whose declared channel count is below the
minimum required by the color mode, so the merged image is no longer read
with more bytes per pixel than were allocated (upstream's channel_idx array
enlargement is not applicable: that write path does not exist in 2.99.8)