Add custom 'marvin' persona as interactive default

Server-only deployment has no console admin API, so the persona is
upserted directly into the SQLite DB via scripts/persona.py with the
prompt text versioned in the repo (VM persistence rules, Gitea/GitHub
remotes, rootless podman). Built-in personas are seeded by migration
063; this sets marvin as the interactive default.

README.md

@@ -104,6 +104,23 @@ Edit `configs/turnstone/config.toml` (gitignored; see
   (currently mirrored from opencode's `auth.json`).
 - `[auth] jwt_secret` — required, generate once.
 - `[database] path` — SQLite on the `data/` share.
+- `[tools]` — `workspace_dir` surfaced to the model
+  (`/home/marvin/work`, mounted from `./work`).
+
+### Personas
+
+Built-ins (Engineer, Writer, Researcher, Scribe, Manager, Executive)
+are seeded by turnstone's migration. This deployment adds a custom
+default persona `marvin` (VM-specific: persistence rules, Gitea remotes,
+podman) via `scripts/persona.py` — the prompt text is versioned there
+and re-applied after a DB reset:
+
+```sh
+python3 scripts/persona.py            # --db data/turnstone.db default
+```
+
+(Without a console deployment, persona CRUD is a direct SQLite write;
+with `turnstone-console` running, use its admin API/Personas tab.)
 
 ## Notes / trade-offs