docs(changelog): add the #1717 fragment

Co-Authored-By: Claude Fable 5.2 <[email protected]>

changelog.d/1717-wind-server-decode.md

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+- The Wind server no longer blocks every other request while it decodes a
+  forecast. Decoding runs on a worker thread (up to 400 ms of blocking down to
+  about 4 ms), and choosing an overlay after wind has loaded fetches only the
+  overlay's field (mazy1998, #1717).