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/noaa.mjs

@@ -57,15 +57,33 @@ export async function briefing() {
       wildfires: fire.length,
       other: other.length,
     },
-    topAlerts: features.slice(0, 15).map(f => ({
-      event: f.properties?.event,
-      severity: f.properties?.severity,
-      urgency: f.properties?.urgency,
-      headline: f.properties?.headline,
-      areas: f.properties?.areaDesc,
-      onset: f.properties?.onset,
-      expires: f.properties?.expires,
-    })),
+    topAlerts: features.slice(0, 15).map(f => {
+      // Extract centroid from GeoJSON geometry
+      let lat = null, lon = null;
+      const geo = f.geometry;
+      if (geo?.type === 'Polygon' && geo.coordinates?.[0]?.length) {
+        const coords = geo.coordinates[0];
+        lat = coords.reduce((s, c) => s + c[1], 0) / coords.length;
+        lon = coords.reduce((s, c) => s + c[0], 0) / coords.length;
+      } else if (geo?.type === 'MultiPolygon' && geo.coordinates?.length) {
+        const coords = geo.coordinates[0][0];
+        lat = coords.reduce((s, c) => s + c[1], 0) / coords.length;
+        lon = coords.reduce((s, c) => s + c[0], 0) / coords.length;
+      } else if (geo?.type === 'Point') {
+        [lon, lat] = geo.coordinates;
+      }
+      return {
+        event: f.properties?.event,
+        severity: f.properties?.severity,
+        urgency: f.properties?.urgency,
+        headline: f.properties?.headline,
+        areas: f.properties?.areaDesc,
+        onset: f.properties?.onset,
+        expires: f.properties?.expires,
+        lat: lat != null ? +lat.toFixed(3) : null,
+        lon: lon != null ? +lon.toFixed(3) : null,
+      };
+    }),
   };
 }