Get the current air quality for a city, from real-time monitoring and atmospheric model data. Use for any "what's the air quality in X", "is it safe to go outside in Y", "how polluted is Z" style question, or whenever pollen/smog/wildfire-smoke/pollution conditions are relevant to a plan (running, cycling, sensitive-groups advice, travel).

city is a free-text place name (e.g. "Bangkok", "Berlin", "Springfield, US").

Returns a dict with:

• location: resolved place name/country/admin1

• us_aqi: the current US Air Quality Index (0-500+)

• aqi_category: plain-language category computed from us_aqi -- "Good" (0-50), "Moderate" (51-100), "Unhealthy for Sensitive Groups" (101-150), "Unhealthy" (151-200), "Very Unhealthy" (201-300), or "Hazardous" (301+); "Unknown" if no AQI could be resolved for that location

• pm2_5, pm10: particulate matter concentrations (ug/m3)

• ozone, nitrogen_dioxide, sulphur_dioxide, carbon_monoxide: trace gas concentrations (ug/m3)

• local_time: the timestamp of the reading, in the location's local time

• attribution