fix: preserve binary theme assets during build

Author: Neikon

MEMORY.md

@@ -48,6 +48,7 @@ This file stores durable project context so future conversations can resume work
 - `gulpfile.js` now lazy-loads ESM-only Gulp plugins and skips optional directories like `dev/fonts/` when they are absent
 - Hidden config generation now filters non-`.txt` files explicitly so builds do not create stray files like `docs/.robots`
 - Theme entries that depended on fragile remote screenshots have been localized into `images/themes/remote-*` and now build into committed assets under `docs/assets/img/themes/`
+- Binary copies for static images now use `fs.promises.copyFile` instead of `gulp.src().pipe(dest())` because the stream path was corrupting some `.webp` assets in `docs/`
 
 ## Architecture Snapshot