The DB-gated e2e suite covered health, seeded reads, and the arrivesAt
whitelist rejection, but never asserted that a valid POST /api/travel
actually transitions to TRAVELLING, that a concurrent second start is
rejected with 409/TRAVEL_ALREADY_ACTIVE, or that a travel completes and
moves the character. Added one test covering all three plus GET
/api/world/current-location reflecting the move, and restores the demo
character to its original location afterward so the suite stays safely
re-runnable.
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