Document the store switcher and multi-store accounts

Gap: the product has a store switcher (dashboard, top-left store name) and the Accounts portal lists every store under Stores, but no page on docs.nextcommerce.com mentions either. llms.txt returns nothing for "switch", "multiple stores" or "multi-store".

How it surfaced: the agent consultation probes for nextcommerce-site#154 (2026-09-16). Every agency persona, on both Claude and Codex, reported the multi-store story as undocumented; one found a store switcher only in a 2021 changelog entry. Agents can only cite what is written, so agencies evaluating NEXT through their AI agent currently get "not documented" for the one question they always ask.

Ask: a short merchant docs page (Start Here or Manage) covering the dashboard switcher, the Accounts portal Stores menu, and how team access works across stores. Once it exists, llms.txt picks it up and the consultation prompt's agency row finds it.

Evidence: probe matrix, agency transcript.

Start in the Start Here or Manage documentation areas and review the dashboard's top-left store-name switcher and the Accounts portal's Stores menu. Use docs/agent-eval/probe-matrix-2026-09-16.md and docs/agent-eval/v0.4/transcript-claude-agency-seedB.md as context. Done means a short page explains switching stores and team access across stores, and llms.txt can surface it.