Document why heph's op-based sync lets most new features (new link types,
read-side queries, optional payload fields) ship without a coordinated
migration across the hub and spokes, and the narrow case — a new required
SQLite column the apply path writes — that does need a hub-first rollout.
Groundwork for the indented/counted project sidebar, which is pure read-side
(existing parent links + a GROUP BY) and needs no migration.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
