Work out arrival times, layovers and tight connections for a multi-leg trip across time zones

# Work out a multi-leg trip itinerary across time zones Input: `itinerary.json`, a list of flight legs in travel order. Each leg has a local departure time (`depart_local`, wall-clock time at the departure airport), the departure and arrival time zones (IANA names) and the block time in minutes. Rules: - Arrival time = departure instant + duration_min, written as wall-clock time in the arrival airport's zone, format `YYYY-MM-DDTHH:MM`. - Use the real time-zone rules for the travel dates, including daylight-saving changes. - Layover = minutes from a leg's arrival to the next leg's departure (real elapsed minutes). - A connection is tight when its layover is under 60 minutes. - total_elapsed_min = real minutes from the first departure to the last arrival. - date_change_legs = the legs whose local arrival date differs from their local departure date, in travel order. Write `out/itinerary.json`: `{"arrivals": {"<leg>": "<YYYY-MM-DDTHH:MM>", ...}, "layovers_min": {"<leg>": <int>, ...}, "tight": [<leg>, ...], "total_elapsed_min": <int>, "date_change_legs": [<leg>, ...]}` `layovers_min` and `tight` are keyed by the leg that arrives before the connection (every leg except the last), and `tight` is in travel order. ## How this run works - Work on your own: nobody will answer questions in this task, and writing to `ask/` counts against the run. - Write only under `out/`. Create `out/` if it is missing. Inputs are synthetic; don't fetch anything from the network. - Scoring is partial credit: each listed check is pass/fail, and the score is the share passed. Numbers are compared to within 0.005 unless the task says otherwise.