Pick the cheaper of two carriers per parcel using dimensional weight, zones and oversize fees

# Pick the cheaper carrier for each parcel Inputs: `parcels.json` (each parcel's length, width and height in inches, weight in pounds, destination zone) and `rates.json` (two carriers' rate cards). Rules, applied per carrier: - Dimensional weight = length x width x height / that carrier's dim_divisor, rounded UP to a whole pound. - Actual weight is rounded UP to a whole pound. - Billable weight = the larger of the rounded actual weight and the dimensional weight. - Price = zone base price (covers the first pound) + per_lb for the zone x (billable weight - 1). - Add the carrier's oversize_fee when the parcel's longest side is over the carrier's oversize_longest_in (strictly greater). - Choose the carrier with the lower price; if both are equal, choose the carrier listed first in rates.json. Write `out/shipping.json`: `{"parcels": {"<parcel_id>": {"billable_lb": {"<carrier>": <int>, ...}, "price_usd": {"<carrier>": <usd>, ...}, "choice": "<carrier>"}, ...}, "total_usd": <sum of chosen prices>}`. ## 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.