fix(fires): paint aggregated heat cells warm by density, not by strongest FRP

Coloring each far-zoom cell with the ramp stop of its strongest detection
turned a burning region into a blue / teal / lime mosaic: neighbouring
cells flipped hue on one outlier and the cold stops did not read as fire.
Cells say where it burns, so they go back to the heat-normalized score
(density, night share, max FRP) on the warm end of the ramp — lime, amber,
red — with the cell card accent matching. Single detections keep the full
six-stop FRP ramp.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

docs/CURRENT-STATE.md

@@ -2058,9 +2058,12 @@ accessible name remains "Don't show this again". Control behavior is unchanged.
 
 Every FIRMS detection is colored by fire radiative power on a six-stop cold →
 hot ramp: blue from 0 MW, teal from 5, lime from 20, amber from 50, orange from
-100 and red from 300 MW (`FRP_RAMP` in `src/data/firmsIntensity.js`). Heat
-cells, glow sprites and card accents read the same ramp; confidence and
-brightness do not affect the color.
+100 and red from 300 MW (`FRP_RAMP` in `src/data/firmsIntensity.js`). Glow
+sprites and fire-card accents read that ramp; confidence and brightness do
+not affect the color. Aggregated heat cells (far zoom) instead take the warm
+end of the ramp — lime, amber or red — from their heat-normalized score
+(density, night share and strongest FRP), so a region reads as one field
+rather than a per-cell mosaic; the cell card's accent matches its fill.
 
 The Active Fires row carries a "Fire intensity (FRP)" slider on a log scale
 whose track is painted with the ramp and ticked at the same six values (its