Fix build-all.sh: deploy platform JS to shared/static/wasm/

build-all.sh was missing the sx-platform.js → sx-platform-2.js copy,
so the served file was stale (still requesting .sxbc.json instead of
.sxbc).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/browser/build-all.sh

@@ -26,6 +26,7 @@ cp dist/sx_browser.bc.wasm.js "$DEST/"
 cp dist/sx_browser.bc.js "$DEST/"
 rm -rf "$DEST/sx_browser.bc.wasm.assets"
 cp -r dist/sx_browser.bc.wasm.assets "$DEST/"
+cp dist/sx-platform.js "$DEST/sx-platform-2.js"
 cp dist/sx/*.sx "$DEST/sx/"
 cp dist/sx/*.sxbc "$DEST/sx/" 2>/dev/null || true
 # Keep assets dir for Node.js WASM tests