ReactiveObject mirrors ReactiveListModel for a single entity. Loads via
GET <baseUrl><source>, stays in sync via Mercure SSE on `topic`, and
exposes the entity's JSON keys on a `data` QQmlPropertyMap so QML reads
them as `obj.data.title` with bindings that re-evaluate on change.
Properties:
- source / topic / baseUrl / token (configuration)
- data (QQmlPropertyMap*) — entity fields
- ready — initial fetch finished
- exists — entity present (false on 404 / delete)
- pending — at least one optimistic mutation in flight
- error
invoke(method, path, body, optimistic) is identical in shape to
ReactiveListModel.invoke(): apply optimistic to `data`, send the
request with an Idempotency-Key, clear `pending` on the matching
Mercure echo, roll back on 4xx/5xx or 10s timeout. The rollback
restores backed-up values and removes keys we added optimistically.
Wired into the QML module; the skeleton builds clean. Used by Phase 3
sub-commit 3's todo edit form.
Includes the merged CI trigger change (workflow now runs on `main`
branch only, not `dev` — keeps Gitea-runner pressure low while we're
iterating on dev).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>