Add build-all.sh, bytecode test mode — 5 failures with SX_TEST_BYTECODE=1

The hydration bug root cause: .sxbc bytecoded modules break effect
closures. Source-loaded modules work (15/15), bytecoded fail (10/15).

Run: SX_TEST_BYTECODE=1 node hosts/ocaml/browser/test_wasm_native.js

Failing: scoped static class, signal attr initial, reactive-spread,
CSSX in island scope, reactive attr update.

Also adds build-all.sh (full WASM pipeline) and sx_build target="wasm"
MCP tool integration.

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

hosts/ocaml/browser/build-all.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+# Full build: OCaml WASM kernel + bundle + bytecode compile + deploy to shared/static/wasm/
+#
+# Usage: bash hosts/ocaml/browser/build-all.sh
+#   Or via MCP: sx_build target="wasm"
+set -e
+cd "$(dirname "$0")"
+
+echo "=== 1. Build WASM kernel ==="
+# Remove assets dir that conflicts with dune's output target
+rm -rf sx_browser.bc.wasm.assets
+eval $(opam env 2>/dev/null)
+cd ..
+dune build browser/sx_browser.bc.wasm.js browser/sx_browser.bc.js bin/sx_server.exe 2>&1
+cd browser
+
+echo "=== 2. Bundle ==="
+bash bundle.sh
+
+echo "=== 3. Compile .sxbc bytecode ==="
+node compile-modules.js dist
+
+echo "=== 4. Deploy to shared/static/wasm/ ==="
+DEST=../../../shared/static/wasm
+cp dist/sx_browser.bc.wasm.js "$DEST/"
+cp dist/sx_browser.bc.js "$DEST/"
+rm -rf "$DEST/sx_browser.bc.wasm.assets"
+cp -r dist/sx_browser.bc.wasm.assets "$DEST/"
+cp dist/sx/*.sx "$DEST/sx/"
+cp dist/sx/*.sxbc "$DEST/sx/" 2>/dev/null || true
+# Keep assets dir for Node.js WASM tests
+cp -r dist/sx_browser.bc.wasm.assets ./ 2>/dev/null || true
+
+echo "=== 5. Run WASM tests ==="
+node test_wasm_native.js
+
+echo "=== Done ==="