Keep weak Active Fires as markers through the hand-off

The 750–3,000 km markers band now draws up to 20,000 detections instead
of 2,500. At the 2,400 km end of the cross-fade the padded view over
Africa holds ~21,000 fires, and the old cap kept only those above
~17 MW, so most heat spots faded into empty ground as the heatmap went
out. A rebuild of that many costs ~60 ms, and only in the densest views.

changelog.d/1426-fire-intensity-filter.md

@@ -5,7 +5,7 @@
   High confidence switch and an "N of M shown" counter to the layer row. Far
   zoom shows a Snap Map–style heatmap in the same colors instead of squares,
   one distinct spot per fire, empty where nothing burns, and cross-fades with
-  the markers around 3,000 km with no gap. The filter applies once before
+  the markers around 3,000 km with no gap, keeping weak fires as markers. The filter applies once before
   rendering, so markers, cards, the heatmap, context and the top-fires query
   agree; share links keep it (`w` token: `f`, `c`), and `get_active_fires`
   takes matching `min_frp_mw` and `confidence` arguments. Default 0 MW / All

docs/CURRENT-STATE.md

@@ -2225,7 +2225,10 @@ built at every zoom and cross-fade by camera height between 2,400 and
 3,600 km, every frame, so a fast zoom never shows a gap: the heatmap fades by
 imagery `alpha` (a hidden Cesium imagery layer is unmapped from the globe
 tiles and re-mapped late when shown), the markers by sprite alpha, and the
-marker collection is hidden once the heatmap is whole. "N FIRES" cards from a 2° / 1° aggregation still label the hottest
+marker collection is hidden once the heatmap is whole. The 750–3,000 km
+markers band draws up to 20,000 detections (the strongest in the padded
+view), so the weak fires the heatmap shows stay on screen as markers when it
+fades out. "N FIRES" cards from a 2° / 1° aggregation still label the hottest
 areas; their accent is the strongest fire's FRP color.
 
 The Active Fires row carries a "Fire intensity (FRP)" slider on a log scale

src/layers/firms/policy.js

@@ -33,10 +33,14 @@ export const LOD_LEVELS = [
     labelDistance: 8500000,
   },
   {
+    // Up to 20,000 markers: at the 2,400 km end of the hand-off the padded
+    // view over Africa, the densest region, holds ~21,000 detections, and a
+    // tighter cap left the heatmap's weak spots dissolving into nothing.
+    // A rebuild of that many costs ~60 ms, only there.
     id: 'local',
     minHeight: 750000,
     mode: 'detections',
-    maxDetections: 2500,
+    maxDetections: 20000,
     labelDistance: 4500000,
   },
   {