Delete ensure_user_for and mint_and_persist_agent_token, the user step
of sync_agent (the per-rebuild re-mint, #4644) and of
forge_after_first_spawn, and the hive-priv WriteAgentForgeToken request
that wrote the token into the agent's state dir. hivectl forge
create-user now refuses an agent and points at swarmctl agent
mint-forge-token. mint_token, ensure_user_exists and TOKEN_SCOPES stay:
provision_user_token and the core bootstrap still call them.
Refs #3782
b5d07d4df2