Two new datasets from the structure benchmark: population growth (World Bank API) and airports (OurAirports)

The structure skill has now been tested on the two source shapes it hadn't seen: a paginated JSON API and a join across several linked tables. Each run produced a new dataset.

• Population growth by country, 1960–2025: the World Bank's annual population growth rate for 217 economies and 48 regional and income-group aggregates, flagged so they aren't summed with countries. A useful catch: the World Bank's country-code field is blank for its five income groups, so the obvious key didn't work.
• Airports with runway summaries: all 86,094 OurAirports sites, each joined to its country and region and to a count and longest length of its runways. Every link between the tables is checked. NA here means North America or Namibia, not missing, so tools that read NA as blank will drop real values.

Both met every hard bar on the first build. The benchmark write-up lists three gaps in the skill. The JSON/API guidance has already been added to the skill; the other two are queued.