SX request handler + AJAX nav + shared JIT globals + shell cleanup

- Remove prism.js, sweetalert2, body.js, sx-browser.js from shell —
  only WASM kernel (sx_browser.bc.wasm.js + sx-platform.js) loads
- Restore request-handler.sx integration: SX handles routing + AJAX
  detection, OCaml does aser → SSR → shell render pipeline
- AJAX fragment support: SX-Request header returns content fragment
  (~14KB) instead of full page (~858KB), cached with "ajax:" prefix
- Fix language/applications/etc page functions to return empty fragment
  instead of nil (was causing 404s)
- Shared JIT VM globals: env_bind hook mirrors ALL bindings to a single
  shared globals table — eliminates stale-snapshot class of JIT bugs
- Add native `parse` function for components that need SX parsing
- Clean up unused shell params (sx-js-hash, body-js-hash, head-scripts,
  body-scripts, use-wasm) from shell.sx, helpers.py, and server.ml

14/32 Playwright tests pass (navigation, SSR, isomorphic, geography).
Remaining failures are client-side (WASM bytecode 404s block hydration).

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

web/request-handler.sx

@@ -43,7 +43,7 @@
 (define
   sx-handle-request
   (fn
-    (path headers env)
+    (path headers env shell-vars)
     (let
       ((is-ajax (or (has-key? headers "sx-request") (has-key? headers "hx-request")))
         (path-expr (sx-url-to-expr path))
@@ -52,44 +52,5 @@
         (nil? page-ast)
         nil
         (let
-          ((nav-path (if (starts-with? path "/sx/") path (str "/sx" path))))
-          (cek-try
-            (fn
-              ()
-              (if
-                is-ajax
-                (let
-                  ((content (list (make-symbol "~layouts/doc") :path nav-path page-ast)))
-                  (render-to-html content env))
-                (let
-                  ((wrapped (list (make-symbol "~layouts/doc") :path nav-path page-ast))
-                    (full-ast
-                      (list
-                        (make-symbol "~shared:layout/app-body")
-                        :content wrapped))
-                    (body-html (render-to-html full-ast env)))
-                  (render-to-html
-                    (list
-                      (make-symbol "~shared:shell/sx-page-shell")
-                      :title "SX"
-                      :csrf ""
-                      :page-sx (serialize full-ast)
-                      :body-html body-html
-                      :component-defs __shell-component-defs
-                      :component-hash __shell-component-hash
-                      :pages-sx __shell-pages-sx
-                      :sx-css __shell-sx-css
-                      :sx-css-classes __shell-sx-css-classes
-                      :asset-url __shell-asset-url
-                      :sx-js-hash __shell-sx-js-hash
-                      :body-js-hash __shell-body-js-hash
-                      :wasm-hash __shell-wasm-hash
-                      :head-scripts __shell-head-scripts
-                      :body-scripts __shell-body-scripts
-                      :inline-css __shell-inline-css
-                      :inline-head-js __shell-inline-head-js
-                      :init-sx __shell-init-sx
-                      :use-wasm true
-                      :meta-html "")
-                    env))))
-            (fn (err) (str "<h1>Render error</h1><pre>" err "</pre>"))))))))
+          ((nav-path (if (and (>= (len path) 4) (= (slice path 0 4) "/sx/")) path (str "/sx" path))))
+          {:page-ast page-ast :nav-path nav-path :is-ajax is-ajax})))))