feat(weather): add satellite cloud filter strength slider

Blend the existing infrared brightness key from Full (0%) to Clouds only (100%), preserving Soft/Vivid as independent opacity presets. Commit filter changes on slider release and retain legacy share-link mode codes.

docs/CURRENT-STATE.md

@@ -256,8 +256,13 @@ Clouds only applies a soft brightness ramp to decoded pixels once, using
 Cesium's sRGB-to-linear conversion (`channel ** 2.2`) and smoothstep from 0.40
 to 0.70. The old 0.55 threshold is the ramp midpoint. RGB and source alpha are
 preserved in Full image mode; both modes use the chosen layer opacity. This
-is a display filter, not a cloud mask. Satellite share links retain the display
-mode; observation history remains transient and links open latest.
+is a display filter, not a cloud mask. The cloud-filter slider is a continuous
+0–100% strength: 0% is Full, 100% is the existing Clouds only key, and
+intermediate values blend their alpha. The value commits on slider release to
+avoid restaging for every pointer event. Satellite share links carry the filter
+strength; legacy `f`/`a` values keep their Clouds only / Full meanings. Soft and
+Vivid remain layer-opacity presets (40%/70%); history remains transient and links
+open latest.
 Global infrared fetches one capped 4 MiB, 2048×1024 mosaic per frame and decodes
 and processes it before staging. Globe hosts crop that canvas into 256 px tiles
 to maximum level 3 on a geographic 2×1 root grid bounded to the manifest extent,
@@ -302,7 +307,8 @@ release commits immediately. Latest selects the newest frame per product, and
 history labels the actual displayed frame as synced or nearest. Missing-frame
 messages use each product's eligibility gap (30 minutes, or three hours for the
 global mosaic). Wind shows forecast valid and issue times and does not follow
-history. Satellite clouds uses Clouds only / Full image configuration labels.
+history. Satellite clouds uses Clouds only / Full controls, a continuous cloud
+filter slider and Soft/Vivid opacity presets in its right-rail settings.
 
 Left weather rows retain only the toggle and one status line with a source
 tooltip. Configuration and the cyclone Storms list live in the cards, as do the