registry-manifest: 15 PublicSchema IRIs used by BReg and Relay fixtures are absent from the draft graph (#589 audit criterion)

## Context

#589 asked for a repository-wide audit of PublicSchema IRIs against the draft graph and was closed by PR #851. The review of that PR found the criterion may be unaddressed: 15 PublicSchema IRIs used by BReg and Relay fixtures are absent from the draft graph in `products/manifest`:

- CivilRegistration
- GroupRole and its five values
- Sex and its three values
- contact
- eventType
- local_identifier

## Acceptance

- Either the graph gains the terms the fixtures use, or the fixtures move to terms the graph defines, or the issue records why fixtures may use terms outside the graph.
- A check that fails when a fixture cites a PublicSchema IRI the graph does not define, so the audit does not drift again.

Start by inspecting the draft graph in products/manifest and the BReg and Relay fixtures that cite the listed PublicSchema IRIs, then review PR #851 and issue #589 for the audit context. Done means the graph and fixtures are consistent or the exception is documented, with a check that fails when a fixture cites an undefined PublicSchema IRI.

Scritto dal modello di indicizzazione a partire dal testo della issue.