…tack

## Summary

### Why?

The e2e suite barely validated anything: pings, a Land that only checked a non-empty sqid, one test that stopped at status `started`, and a thin cancel smoke test with a standing TODO. It also could not exercise the full pipeline, because `service/submitqueue/docker-compose.yml` did not include runway — the orchestrator blocks on runway's merge-conflict-check and merge signals, so every request stalled at `started`.

### What?

Add `runway-service` to `service/submitqueue/docker-compose.yml`, sharing the existing `mysql-queue` (no app DB). Runway already publishes SUCCEEDED signals via its Merger extension (the noop merger wired in `service/runway/server`), so with it in the stack a request now flows all the way to `landed`.

Add a reusable e2e harness (`test/e2e/submitqueue/harness_test.go`): `land`, `awaitStatus`, `awaitTerminal`, `timeline` + `assertStatusesInOrder` (white-box ordered `request_log` status history, tolerant subsequence), `terminalState` (white-box internal `RequestState` from the operating store), and `lastError` — so new per-stage and error-path tests drop in as a few lines.

Rewrite the suite: `TestLand_HappyPath_ReachesLanded` drives a request to terminal success and asserts three views — the black-box `landed` Status, the ordered status history `accepted → started → batched → scored → landed`, and the operating store's internal `RequestStateLanded` (this also covers the request-log ownership invariant: every status but the synchronous `accepted` reaches storage only via the orchestrator-publishes / gateway-persists log path). The pings and graceful-shutdown checks are kept. The cancel test asserts the deterministic half (Cancel returns OK and the gateway synchronously records the `cancelling` intent). Asserting terminal `cancelled` is racy — a cancel processed before the orchestrator's start controller creates the request is rejected to the DLQ and reconciled to `error` — and needs a pipeline-pause lever, deferred to the next per-stage increment.

## Test Plan

✅ `make e2e-test` — full Docker stack (gateway + orchestrator + runway + 2 MySQL) passes; a request reaches `landed` end to end.
✅ `make fmt`; `make check-gazelle` / `make check-tidy` verified clean (only intended edits).