feat: add maps_air_quality tool

[cablate]

Summary

• New maps_air_quality tool — AQI index, pollutant concentrations, and health recommendations by demographic group
• Global coverage including Japan (unlike Weather API)
• 7 demographic health recommendations: general, elderly, lung disease, heart disease, athletes, pregnant women, children
• Optional individual pollutant data: PM2.5, PM10, NO2, O3, CO, SO2
• All 9 files synced per Tool Change Checklist (13 → 14 tools)

API

• Endpoint: POST https://airquality.googleapis.com/v1/currentConditions:lookup
• Price: $0.005/request ($5/1000 calls)
• Prerequisite: Enable Air Quality API in Google Cloud Console

Test evidence

exec air-quality '{"latitude":35.6762,"longitude":139.6503}' → AQI 75 "Good" (Tokyo)
exec air-quality '{"latitude":37.422,"longitude":-122.0841}' → AQI 87 "Excellent" (Mountain View)
exec air-quality '{"latitude":35.6762,"longitude":139.6503,"includePollutants":true}' → 6 pollutants returned

Test plan

• npm run build passes
• exec air-quality returns valid AQI data
• smoke test expectedTools includes maps_air_quality
• README tool count updated to 14
• SKILL.md Tool Map includes air-quality

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