New docs/user/cluster.md — the practical companion to cluster-config.md's
reference: zero-to-served walkthrough (validate/import/plan/apply, derived
roots, data loading, --cluster serving), the day-2 edit->plan->apply->restart
loop with a per-change-kind table, drift observation and convergence, the
approval gate for destructive changes, crash/lock/lost-ledger recovery, the
boot-refusal table with remedies, deployment patterns (replicas, backup
unit, CI gating), and the explicit not-yet list (hot reload, S3-hosted
cluster dirs, per-query exposure, pipelines). Linked from the user index,
the agent guide's topic map, and cross-linked from the reference.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
