Add PostGraphile, Grafast and Apollo project notebook

[sdairs]

Adds Common Ground, a two-workspace project/task notebook built with PostGraphile 5, Grafast and Apollo Client on ClickHouse Managed Postgres. SQL foreign keys generate the nested API; verified synthetic-account sessions select transaction-local member/workspace settings, and Postgres RLS plus composite foreign keys enforce reads and writes. The browser includes real cursor pagination, generated mutations and a fresh Apollo cache on workspace changes.

Includes source, locked dependencies, generated schema, README, actual managed-browser screenshot and scoped CI. Local and managed Postgres validation passed typecheck/build, 3 unit checks, 7 API/role checks and 2 browser tests. Coverage includes nested/forged-scope isolation, privilege denials, connection pagination beyond both page sizes, cross-workspace insert/update controls and unchanged foreign rows, and Grafast pool-setting reset. Supplied-CA TLS worked; unrelated CA and a reachable incorrect URL hostname were rejected. A real app restart preserved the verified session, project, three tasks and completed checkbox. The owned disposable managed fixture was deleted and its absence verified; the isolated development VM is stopped.

This is a local synthetic-account example. Companion article remains a separate local draft for editorial review.