feat(fires): FRP intensity filter, confidence switch and six-stop color ramp (HAL-676)

Color every FIRMS detection by fire radiative power on the Portolan
cold → hot ramp (blue · teal · lime · amber · orange · red at
0 · 5 · 20 · 50 · 100 · 300 MW), replacing the three warm stops that
made a 2 MW and a 40 MW fire look alike. Heat cells, glow sprites and
card accents all read the same ramp (src/data/firmsIntensity.js).

Add a minimum-FRP log slider whose track is painted with the ramp (so
it doubles as the legend), an All / Nominal+ / High confidence switch
and an "N of M shown" counter to the Active Fires row. The filter runs
once in ingestion.applyFilter(), so markers, cards, heat cells, the
context store, the top-fires query and the analyst records all see one
set. Default is 0 MW / All: many of the strongest fires are rated low.

Persist both options in the layer state (token w: minFrp `f`,
confidence `c`), including the short share codec, and give the agent's
get_active_fires tool matching min_frp_mw / confidence arguments.

Layer panel gains generic `slider` and `segmented` row descriptors
(src/ui/rowFilterControls.js). New strings in es / ru / zh-CN.

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

src/share/viewCodec.js

@@ -255,6 +255,7 @@ export const SHARE_VIEW_FLAGS = freezeAll([
  * written explicitly.
  */
 export const SHARE_VIEW_LAYER_OPTION_ABSENT = Object.freeze({
+  'local-firms': Object.freeze({ minFrp: 0, confidence: 'all' }),
   traffic: Object.freeze({ roadMode: null }),
   'weather-lightning': Object.freeze({ opacity: 'strong' }),
   'weather-radar': Object.freeze({ opacity: 'strong' }),