Add a sync-project-tree workflow that regenerates this repo's tracked-file
tree and opens (or force-updates) a PR against RunicGateway/docs whenever the
layout on main changes. Never writes to the docs repo's main directly. Reuses
the existing REGISTRY_USER / REGISTRY_TOKEN secrets. Tree rendering lives in
.gitea/scripts/gen_tree.py (deterministic, dirs-first ordering).
Co-Authored-By: Claude <noreply@anthropic.com>
