Double the far-zoom heat spots so they read as spots

At 10 km per pixel each fire was a marker-sized spot that faded into the
imagery from the globe view. A 2048 px grid with the same one-pixel blur
makes every spot exactly twice as wide (~60 km for a lone weak fire),
still separate, and the build is three times faster.

docs/CURRENT-STATE.md

@@ -2185,10 +2185,10 @@ accents read that ramp; confidence and brightness do not affect the color.
 
 At far zoom (camera above ~3,000 km) the layer drapes a Snap Map–style
 heatmap instead of individual markers: the shown detections are binned on a
-global 4096 × 2048 grid (≈10 km per pixel), each weighted by its FRP in megawatts (so heat is
+global 2048 × 1024 grid (≈20 km per pixel), each weighted by its FRP in megawatts (so heat is
 radiated power, and raising the FRP slider does not dim areas where strong fires
-burn), Gaussian-blurred by one pixel so each fire stays a spot about the size
-of its marker,
+burn), Gaussian-blurred by one pixel so each fire stays a distinct spot about
+twice the size of its marker,
 normalized on a log scale against the 99.5th percentile and mapped through the
 same hues, from a bright red edge through orange and gold to a pale
 white-hot core. The edge starts more than half opaque, so regions far below