PR #112 bumped PKGVER/UPSTREAM_TAG to 1.2.4 but left LMCP_TARBALL_SHA256 at the
1.2.3 hash, so the sha256 -c check failed on the v1.2.4 tarball and lmcp-debian
errored. Update the pinned hash to the v1.2.4 archive.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>