feat(wind): add keyless NOAA GFS wind layer with animated particles

Add a Wind layer animating the global 10 m wind field from NOAA GFS.

The /api/wind 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° default), and serves a manifest plus a Float32
U/V payload cached per cycle for an hour (single-flight, last-good on failure).

The client renders nullschool-style particles in a canvas overlay: bilinear
field sampling with longitude wrap, per-frame advection, Cesium camera
projection, and globe-occlusion culling via EllipsoidalOccluder.

Validated end-to-end against the real 2026-09-14 06z cycle on Node 25
(180x91 grid at 2°, 131,040-byte payload, plausible mean |u|/|v|). The WASM
decoder requires Node >=24, which the repo already requires.

Registered as `wind` (token k) with attribution and docs. Verified: npm test
(3412 pass, 0 fail), npm run check:boundaries.

server/providers/wind/decode.js

@@ -0,0 +1,63 @@
+import os from 'node:os';
+import path from 'node:path';
+import { promises as fs } from 'node:fs';
+import { randomUUID } from 'node:crypto';
+
+/**
+ * Lazily created ecCodes WASM instance. The `@meri-imperiumi/eccodes-wasm`
+ * module is only imported on first use so unit tests can inject a fake
+ * decoder without loading the WASM (which requires Node >= 24).
+ * @type {?Promise<object>}
+ */
+let eccodesPromise = null;
+
+/** @returns {Promise<object>} The shared ecCodes WASM instance. */
+function loadEccodes() {
+  eccodesPromise ??= (async () => {
+    const module = await import('@meri-imperiumi/eccodes-wasm');
+    return module.createEccodes();
+  })();
+  return eccodesPromise;
+}
+
+/**
+ * Decode one GRIB2 wind message into its grid metadata and values.
+ *
+ * The WASM decoder reads from its own mounted filesystem, so the message is
+ * written to a temp file under `mountDir` and removed in `finally`.
+ *
+ * @param {Buffer} buffer - One GRIB2 message (already byte-range extracted).
+ * @param {{ eccodesModule?: object, mountDir?: string }} [options]
+ * @returns {Promise<{ni: number, nj: number, lo1: number, la1: number,
+ *   di: number, dj: number, values: ArrayLike<number>, shortName: string,
+ *   level: number, units: string}>}
+ */
+export async function decodeWindGribMessage(
+  buffer,
+  { eccodesModule, mountDir = os.tmpdir() } = {},
+) {
+  const eccodes = eccodesModule ?? (await loadEccodes());
+  const name = `wind-${randomUUID()}.grib2`;
+  const file = path.join(mountDir, name);
+  await fs.writeFile(file, buffer);
+  let handle = null;
+  try {
+    eccodes.mountFilesystem(mountDir);
+    handle = eccodes.openGrib(file);
+    return {
+      ni: handle.getLong('Ni'),
+      nj: handle.getLong('Nj'),
+      lo1: handle.getDouble('longitudeOfFirstGridPointInDegrees'),
+      la1: handle.getDouble('latitudeOfFirstGridPointInDegrees'),
+      di: handle.getDouble('iDirectionIncrementInDegrees'),
+      dj: handle.getDouble('jDirectionIncrementInDegrees'),
+      values: handle.getDoubleArray('values'),
+      shortName: handle.getString('shortName'),
+      level: handle.getLong('level'),
+      units: handle.getString('units'),
+    };
+  } finally {
+    if (handle) handle.delete();
+    await fs.unlink(file).catch(() => {});
+  }
+}