VM: closure env chain for GLOBAL_GET/SET + remove JIT skip

vm_closure now stores the original closure env (vm_closure_env).
GLOBAL_GET walks the closure env chain when the variable isn't in
vm.globals. GLOBAL_SET writes to the correct env in the chain.

This enables JIT compilation of all named functions regardless of
closure depth. No more closure skip check needed.

Pre-compile time back to ~7s (was 37s with closure skip).

Note: sx-parse sibling list parsing still has issues — the root
cause is in how the JIT-compiled letrec + OP_CLOSURE interacts
with the upvalue cell mechanism. Investigation ongoing.

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

shared/sx/ocaml_bridge.py

@@ -440,16 +440,6 @@ class OcamlBridge:
                         _logger.warning("OCaml load skipped %s: %s",
                                         filepath, e)
 
-                # sx-parse has deeply nested letrec + define inside fn
-                # bodies. The JIT closure/upvalue mechanism can't handle
-                # the multiple nesting layers correctly — nested list
-                # parsing produces wrong results. Force CEK.
-                try:
-                    await self._send('(vm-reset-fn "sx-parse")')
-                    await self._read_until_ok(ctx=None)
-                except OcamlBridgeError:
-                    pass
-
                 # SSR overrides: effect is a no-op on the server (prevents
                 # reactive loops during island SSR — effects are DOM side-effects)
                 try: