chore: sync main into chore/sync-main-with-dev (strategy ours)

Absorb main's v0.4.21 squash node (4ebe078) without bringing in any of its
content — main's logical content is already in dev's later commits. This
fixes the ancestry-divergence conflict so the subsequent dev → main
promote PR is mergeable.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: enriquephl