Merge wind and ECMWF candidates into walkthrough train

DATA_SOURCES.md

@@ -15,6 +15,7 @@ How to read this:
 
 | Source                                                                | Used for                                                                                                                            | License / terms                                                                                                                                                                                                                                                                                                                                       | Attribution                                                                                                                                 |
 | --------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------- |
+| **NOAA GFS (wind)** | Global 10 m wind field for the animated Wind layer | U.S. public domain (NOAA); keyless via NOAA Open Data on AWS | "NOAA Global Forecast System (GFS)" (courtesy; not an endorsement) |
 | **OpenStreetMap ALPR camera locations** (including DeFlock community mapping) | Optional mapped automatic license-plate-reader camera layer | [ODbL 1.0](https://opendatacommons.org/licenses/odbl/1-0/); commercial use permitted with applicable attribution and database share-alike obligations | [© OpenStreetMap contributors](https://www.openstreetmap.org/copyright); [DeFlock](https://deflock.org) community mapping |
 | **Google Map Tiles API** (Photorealistic 3D Tiles) + Places/Geocoding | The 3D globe, voice scene context, and on-demand nearby installation search                                                         | Google Maps Platform ToS (proprietary, your own key + billing)                                                                                                                                                                                                                                                                                        | "Google" / "Google Maps" logo — **shown in-app**, required                                                                                  |
 | **OpenSky Network**                                                   | Primary worldwide live-flight snapshot                                                                                              | Non-commercial research/education license                                                                                                                                                                                                                                                                                                             | Schäfer et al., _"Bringing Up OpenSky"_, IPSN 2014 + opensky-network.org                                                                    |
@@ -153,6 +154,24 @@ transaction quota. Requires a free `FIRMS_MAP_KEY`
 (https://firms.modaps.eosdis.nasa.gov/api/map_key/); the layer is empty without it.
 The former bundled 2026-05-25 snapshot was removed 2026-07-16.
 
+### ECMWF IFS wind
+
+Wind also offers ECMWF IFS 10 m forecasts from the keyless [ECMWF Open Data](https://www.ecmwf.int/en/forecasts/datasets/open-data) service. The proxy reads its JSON Lines inventory and fetches only 10u/10v GRIB messages, resampling the forecast to the display grid. Data is licensed under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). The [ECMWF Terms of Use](https://apps.ecmwf.int/datasets/licences/general/) also apply. In-app attribution identifies this service as based on ECMWF data and products, links the CC BY 4.0 licence, identifies resampling and animation as modifications, and retains the required ECMWF liability disclaimer. Both model issue time and the selected forecast valid time appear in the layer row. These are model forecasts, not observations.
+
+### NOAA GFS wind
+
+The optional **Wind** layer animates the global 10 m wind field from NOAA's
+Global Forecast System (GFS). The `/api/wind` server-side proxy selects the
+latest available 0.25° cycle, reads its `.idx` inventory, byte-range fetches only
+the `UGRD`/`VGRD` 10 m GRIB2 messages (≈1 MB each instead of the whole ~500 MB
+file), decodes them with ecCodes (WASM), resamples to a compact grid (1° by
+default), and serves a manifest plus a Float32 U/V payload. It is keyless, cached
+per cycle for an hour, and is a **forecast, not an observation**: the particles
+show model flow, not measured wind. Rendering is a 2D canvas particle overlay
+advected by the field and projected through the Cesium camera; globe-occluded
+particles are skipped. NOAA GFS data is U.S. public domain; the credit above is a
+courtesy and does not imply endorsement.
+
 ### Natural Earth physical regions (`natural_earth/`)
 
 Curated from the **Natural Earth 10m physical vectors** (https://www.naturalearthdata.com/ —