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>

hosts/ocaml/bin/mcp_tree.ml

@@ -581,7 +581,8 @@ let rec handle_tool name args =
     in
     let cmd = match target with
       | "ocaml" ->
-        Printf.sprintf "cd %s/hosts/ocaml && eval $(opam env 2>/dev/null) && dune build 2>&1" project_dir
+        let abs_project = if Filename.is_relative project_dir then Sys.getcwd () ^ "/" ^ project_dir else project_dir in
+        Printf.sprintf "cd %s/hosts/ocaml && eval $(opam env 2>/dev/null) && dune build 2>&1 && cp _build/default/browser/sx_browser.bc.wasm.js %s/shared/static/wasm/sx_browser.bc.wasm.js && cp _build/default/browser/sx_browser.bc.js %s/shared/static/wasm/sx_browser.bc.js && cp -r _build/default/browser/sx_browser.bc.wasm.assets %s/shared/static/wasm/" abs_project abs_project abs_project abs_project
       | "js" | _ ->
         let extra = if full then " --extensions continuations --spec-modules types" else "" in
         Printf.sprintf "cd %s && python3 hosts/javascript/cli.py%s --output shared/static/scripts/sx-browser.js 2>&1" project_dir extra