JIT allowlist + integration tests + --test mode + clean up debug logging

JIT allowlist (sx_server.ml):
- Replace try-every-lambda strategy with StringSet allowlist. Only
  functions in the list get JIT compiled (compiler, parser, pure transforms).
  Render functions that need dynamic scope skip JIT entirely — no retry
  overhead, no silent fallbacks.
- Add (jit-allow name) command for dynamic expansion from Python bridge.
- JIT failures log once with "[jit] DISABLED fn — reason" then go silent.

Standalone --test mode (sx_server.ml):
- New --test flag loads full env (spec + adapters + compiler + signals),
  supports --eval and --load flags. Quick kernel testing without Docker.
  Example: dune exec bin/sx_server.exe -- --test --eval '(len HTML_TAGS)'

Integration tests (integration_tests.ml):
- New binary exercising the full rendering pipeline: loads spec + adapters
  into a server-like env, renders HTML via both native and SX adapter paths.
- 26 tests: HTML tags, special forms (when/if/let), letrec with side
  effects, component rendering, eval-expr with HTML tag functions.
- Would have caught the "Undefined symbol: div/lake/init" issues from
  the previous commit immediately without Docker.

VM cleanup (sx_vm.ml):
- Remove temporary debug logging (insn counter, call_closure counter,
  VmClosure depth tracking) added during debugging.

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

hosts/javascript/platform.py

@@ -1131,7 +1131,12 @@ PRIMITIVES_JS_MODULES: dict[str, str] = {
   PRIMITIVES["emitted"] = sxEmitted;
   // Aliases for aser adapter (avoids CEK special form conflict on server)
   var scopeEmit = sxEmit;
-  var scopePeek = sxEmitted;
+  function scopePeek(name) {
+    if (_scopeStacks[name] && _scopeStacks[name].length) {
+      return _scopeStacks[name][_scopeStacks[name].length - 1].value;
+    }
+    return NIL;
+  }
   PRIMITIVES["scope-emit!"] = scopeEmit;
   PRIMITIVES["scope-peek"] = scopePeek;
 ''',