Cache-bust wasm scripts, fix orchestration.sx paren balance

- Add wasm_hash (MD5 of sx_browser.bc.js) to shell template
- Script tags: /wasm/sx_browser.bc.js?v={hash}, /wasm/sx-platform.js?v={hash}
- Pass wasm_hash through helpers.py and ocaml_bridge.py
- Fix missing close paren in bind-sse-swap (broke SX parsing)

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

shared/sx/helpers.py

@@ -7,6 +7,7 @@ page elements (headers, search, etc.) from template context.
 from __future__ import annotations
 
 import hashlib
+import os
 from pathlib import Path
 from typing import Any
 
@@ -884,12 +885,14 @@ def _get_shell_static() -> dict[str, Any]:
         sx_css_classes=sx_css_classes,
         sx_js_hash=_script_hash("sx-browser.js"),
         body_js_hash=_script_hash("body.js"),
+        wasm_hash=_wasm_hash("sx_browser.bc.js"),
         asset_url=_ca.config.get("ASSET_URL", "/static"),
         head_scripts=_shell_cfg.get("head_scripts"),
         inline_css=_shell_cfg.get("inline_css"),
         inline_head_js=_shell_cfg.get("inline_head_js"),
         init_sx=_shell_cfg.get("init_sx"),
         body_scripts=_shell_cfg.get("body_scripts"),
+        use_wasm=os.environ.get("SX_USE_WASM") == "1",
     )
 
     t1 = time.monotonic()
@@ -1081,8 +1084,11 @@ def sx_page_streaming_parts(ctx: dict, page_html: str, *,
     # Tail: bootstrap suspense resolver + scripts + close
     tail = (
         _SX_STREAMING_BOOTSTRAP + '\n'
-        f'<script src="{asset_url}/scripts/sx-browser.js?v={sx_js_hash}"></script>\n'
-        f'<script src="{asset_url}/scripts/body.js?v={body_js_hash}"></script>\n'
+        + (f'<script src="{asset_url}/wasm/sx_browser.bc.wasm.js"></script>\n'
+           f'<script src="{asset_url}/wasm/sx-platform.js"></script>\n'
+           if os.environ.get("SX_USE_WASM") == "1" else
+           f'<script src="{asset_url}/scripts/sx-browser.js?v={sx_js_hash}"></script>\n')
+        + f'<script src="{asset_url}/scripts/body.js?v={body_js_hash}"></script>\n'
     )
 
     return shell, tail
@@ -1120,6 +1126,18 @@ def _script_hash(filename: str) -> str:
     return _SCRIPT_HASH_CACHE[filename]
 
 
+def _wasm_hash(filename: str) -> str:
+    """Compute MD5 hash of a static wasm file, cached for process lifetime."""
+    key = "wasm/" + filename
+    if key not in _SCRIPT_HASH_CACHE:
+        try:
+            data = (Path(__file__).resolve().parent.parent / "static" / "wasm" / filename).read_bytes()
+            _SCRIPT_HASH_CACHE[key] = hashlib.md5(data).hexdigest()[:8]
+        except OSError:
+            _SCRIPT_HASH_CACHE[key] = "dev"
+    return _SCRIPT_HASH_CACHE[key]
+
+
 def _get_csrf_token() -> str:
     """Get the CSRF token from the current request context."""
     try: