How should a script seed chat messages into a document? #165

Problem

docs.plus has per-heading chat. The REST API has no chat surface, so a demo or a test fixture cannot create chat messages through it.

A chat author has to be a real user row, so seeding needs service-role access either way.

What to decide

Either add a chat write path to the REST API, or write and document a service-role seed script.

Acceptance

• One path is chosen and documented.
• A demo document can be seeded with chat messages by following that document.

Notes

A chat author is a grant, not a label: it must be a real user id, and only a service-role caller may set it.