libcppad-dev is declared Multi-Arch: same, but fails to coinstall.

The file /usr/include/cppad/configure.hpp is shared by libcppad-dev
version 2025.00.00.2-1 as present in trixie and version 2026.00.00.0-2
as present in forky|unstable with varying content.

Please ensure that shared files have bit-identical content across
architectures, move architecture-dependent files to
architecture-dependent paths or remove the Multi-Arch: same field.

Kind regards

Helmut Grohne