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>