run metadata update schema

we need to be able to cater for title/users/rbnum/vetos to be able to change mid-run.

The issue names run metadata fields—title, users, rbnum, and vetos—but does not identify files, entry points, or tests. Start by locating the run metadata schema and its update path, then clarify how each field should change mid-run. Done means the schema and update behavior support the requested fields without interrupting an active run.

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