Add zoom-aware symbology, fix globe popovers, expand geo coverage (#34)

* Add zoom-aware symbology, fix globe popovers, expand geo coverage

Map rendering improvements based on user feedback:
- Globe markers now scale with camera altitude (onZoom hook)
- Priority-based visibility culls low-priority markers at world view
- Globe popovers use getScreenCoords for accurate positioning
- Flat map labels hidden at low zoom, revealed progressively
- Default globe altitude lowered from 2.5 to 1.8 for better fill
- Americas region zoom tightened to CONUS focus

Geographic coverage expansion:
- 4 new OpenSky air theaters: Caribbean, Gulf of Guinea, Cape Route, Horn of Africa
- Flight corridors now span Americas and Africa
- NOAA alerts extract centroid lat/lon from GeoJSON geometry
- EPA RadNet stations geocoded with hardcoded coords for 10 US cities
- ISS + Tiangong positions estimated from TLE orbital elements
- GDELT geoEvents() now called in briefing for mapped event points
- New legend entries: Weather Alert, EPA RadNet, Space Station, GDELT Event

* Fix null-safe coordinate checks and remove injected data blob

- Use `!= null` instead of truthy checks for lat/lon in noaa.mjs
  and inject.mjs so valid 0-coordinates (equator/prime meridian)
  are not silently dropped
- Reset jarvis.html `let D` back to null placeholder so generated
  runtime data is not part of the PR diff

* Remove re-injected data blob from jarvis.html

Reset let D back to null — previous commit was correct but
inject.mjs build verification re-injected the payload.

apis/sources/opensky.mjs

@@ -57,6 +57,10 @@ const HOTSPOTS = {
   baltics: { lamin: 53, lomin: 19, lamax: 60, lomax: 29, label: 'Baltic Region' },
   southChinaSea: { lamin: 5, lomin: 105, lamax: 23, lomax: 122, label: 'South China Sea' },
   koreanPeninsula: { lamin: 33, lomin: 124, lamax: 43, lomax: 132, label: 'Korean Peninsula' },
+  caribbean: { lamin: 18, lomin: -90, lamax: 30, lomax: -72, label: 'Caribbean' },
+  gulfOfGuinea: { lamin: -2, lomin: -5, lamax: 8, lomax: 10, label: 'Gulf of Guinea' },
+  capeRoute: { lamin: -38, lomin: 12, lamax: -28, lomax: 24, label: 'Cape Route' },
+  hornOfAfrica: { lamin: 5, lomin: 40, lamax: 15, lomax: 55, label: 'Horn of Africa' },
 };
 
 // Briefing — check hotspot regions for flight activity