test: add isolated production acceptance harness

docs/ACCEPTANCE.md

@@ -18,3 +18,17 @@ npm run acceptance -- --execute-rollback
 The first command is read-only. The mutation flags require every read-only
 check to pass, dispatch a controlled exact-SHA workflow with a unique request
 ID, and wait for matching status plus a successful health endpoint.
+
+## Isolated production acceptance
+
+`npm run acceptance:isolated` provisions disposable bare Git remotes, working
+trees, server appdata folders, Compose definitions, deployment keys,
+configuration migrations and release manifests below the operating-system temp
+directory. It covers clean and portable installs, the 0.10.0 migration path,
+both authentication modes, exact-SHA server pull and Direct Copy, adoption,
+external updates, deploy-key lifecycle, host-key changes, unhealthy activation,
+rollback, network interruption, shutdown recovery, stale plans, corrupt config,
+release integrity and inventories of more than twenty workloads.
+
+Every fixture is removed after its test. The suite never discovers or mutates
+real project folders, configured servers, credentials, containers or releases.