test: add local 2x2 route topology

e2e/README.md

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+# Local 2×2 route E2E
+
+This harness runs one bot-free control stack plus four isolated data-node
+Compose projects. Every data node contains its own qBittorrent, Syncthing, and
+archive-client containers and its own bind-mounted config, secrets, state,
+backup, qB data, and sync roots. The stacks share only the explicitly named
+`archive-control-e2e` network.
+
+The initial scenario starts with no route folders. With the control policy set
+to `eager_mesh`, two cache and two archive registrations must produce four
+independent, bidirectionally verified Syncthing routes. The assertion talks to
+the loopback-only test adapter through a curl sidecar sharing the control
+container's network namespace; Telegram is not initialized.
+
+Run from the archive-clients checkout:
+
+```bash
+./e2e/scripts/up.sh
+./e2e/scripts/logs.sh
+./e2e/scripts/down.sh
+```
+
+`up.sh` defaults `ARCHIVE_CONTROL_SOURCE` to the sibling playground
+`mogic-bot/mogic-repo` checkout. Set that environment variable to test another
+control worktree. `E2E_WAIT_SECONDS` overrides the 360-second assertion
+deadline. `down.sh` removes only the five exact Compose projects and the
+labelled E2E network; it intentionally retains all bind-mounted runtime state.
+
+The Syncthing 2.1.2 and LinuxServer qBittorrent multi-platform image indexes are
+digest-pinned. Runtime secrets are generated with mode 0600 and ignored by
+Git. The qBittorrent test config limits its authentication bypass to the
+isolated E2E network and must never be reused for deployment.