[finish] Customers section: operator manages every customer

Terminal analytical phase: verify every build subtask has completed and resolved, optionally note UI acceptance evidence, then settle. Dispatched as a read-only runner role (feat/finish-as-runner, ADR-0040) whose settle is server-computed (`task.settle` declaring a `finish` terminal) — the server derives the full finish report and flips this child `-> done`; the runner attests nothing. Readied by the fan-out sweep like its siblings; its dependency edges to every coder keep `dispatchable_tasks` from dispatching it until those deps are done.

All 9 coders merged and deployed, and Customers works on dev (Wealthcharts' deletes show in History). Gaps filed as follow-ups: 6119 (org creation not audited, subscription.deleted, duplicate row, MRR) and 6120 (23 UX fixes).