Enrich metadata in `.vt/state.json`

[nbbaier]

Currently, the metadata stored in .vt/state.json is somewhat limited. It shows:

{
  "val": { "id": "uuid-here" },
  "branch": {
    "id": "uuid-here",
    "version": 0
  },
  "lastRun": {
    "pid": 12345,
    "time": "2026-07-09T12:34:56.789Z"
  }
}

I think it'd be useful if at least branch had a field for name. This would allow users to access this information without an API call.