chore: regenerate codemeta.json to version 0.4.0

codemeta.json was stale at version 0.0.0.9000; regenerated using
codemetar::write_codemeta() to sync with current DESCRIPTION (0.4.0).

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

Author: bbuchsbaum