Fix WASM kernel deploy: 3.6MB js_of_ocaml → 68KB wasm_of_ocaml

The deployed sx_browser.bc.wasm.js was actually the js_of_ocaml output
(pure JS), not the wasm_of_ocaml loader. Nothing synced the correct
build output from _build/ to shared/static/wasm/.

- sx_build target=ocaml now auto-syncs WASM kernel + JS fallback + assets
- sx-build-all.sh syncs after dune build
- Correct 68KB WASM loader replaces 3.6MB JS imposter

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

scripts/sx-build-all.sh

@@ -6,6 +6,15 @@ cd "$(dirname "$0")/.."
 
 echo "=== OCaml build ==="
 (cd hosts/ocaml && eval $(opam env 2>/dev/null) && dune build) || { echo "FAIL: OCaml build"; exit 1; }
+
+echo "=== Sync WASM kernel to shared/static/wasm/ ==="
+OCAML_BUILD=hosts/ocaml/_build/default/browser
+cp "$OCAML_BUILD/sx_browser.bc.wasm.js" shared/static/wasm/sx_browser.bc.wasm.js
+cp "$OCAML_BUILD/sx_browser.bc.js" shared/static/wasm/sx_browser.bc.js
+cp -r "$OCAML_BUILD/sx_browser.bc.wasm.assets" shared/static/wasm/
+echo "  WASM loader: $(du -sh shared/static/wasm/sx_browser.bc.wasm.js | cut -f1)"
+echo "  JS fallback: $(du -sh shared/static/wasm/sx_browser.bc.js | cut -f1)"
+
 echo "=== JS browser build ==="
 python3 hosts/javascript/cli.py --output shared/static/scripts/sx-browser.js || { echo "FAIL: JS build"; exit 1; }
 echo "=== JS test build ==="