Add .sxbc MIME type to OCaml HTTP server static file handler

Stops 404s for bytecoded module files — the server now serves .sxbc
files with the correct content type.

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

hosts/ocaml/bin/sx_server.ml

@@ -1639,6 +1639,7 @@ let mime_type_of path =
   else if Filename.check_suffix path ".woff2" then "font/woff2"
   else if Filename.check_suffix path ".woff" then "font/woff"
   else if Filename.check_suffix path ".sx" then "text/sx; charset=utf-8"
+  else if Filename.check_suffix path ".sxbc" then "text/sx; charset=utf-8"
   else "application/octet-stream"
 
 let static_cache : (string, string) Hashtbl.t = Hashtbl.create 256