Complete Python eval removal: epoch protocol, scope consolidation, JIT fixes

Route all rendering through OCaml bridge — render_to_html no longer uses
Python async_eval. Fix register_components to parse &key params and &rest
children from defcomp forms. Remove all dead sx_ref.py imports.

Epoch protocol (prevents pipe desync):
- Every command prefixed with (epoch N), all responses tagged with epoch
- Both sides discard stale-epoch messages — desync structurally impossible
- OCaml main loop discards stale io-responses between commands

Consolidate scope primitives into sx_scope.ml:
- Single source of truth for scope-push!/pop!/peek, collect!/collected,
  emit!/emitted, context, and 12 other scope operations
- Removes duplicate registrations from sx_server.ml (including bugs where
  scope-emit! and clear-collected! were registered twice with different impls)
- Bind scope prims into env so JIT VM finds them via OP_GLOBAL_GET

JIT VM fixes:
- Trampoline thunks before passing args to CALL_PRIM
- as_list resolves thunks via _sx_trampoline_fn
- len handles all value types (Bool, Number, RawHTML, SxExpr, Spread, etc.)

Other fixes:
- ~cssx/tw signature: (tokens) → (&key tokens) to match callers
- Minimal Python evaluator in html.py for sync sx() Jinja function
- Python scope primitive stubs (thread-local) for non-OCaml paths
- Reader macro resolution via OcamlSync instead of sx_ref.py

Tests: 1114 OCaml, 1078 JS, 35 Python regression, 6/6 Playwright SSR

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

shared/sx/async_eval.py

@@ -423,23 +423,39 @@ async def _asf_define(expr, env, ctx):
 
 
 async def _asf_defcomp(expr, env, ctx):
-    from .ref.sx_ref import sf_defcomp
-    return sf_defcomp(expr[1:], env)
+    # Component definitions are handled by OCaml kernel at load time.
+    # Python-side: just store a minimal Component in env for reference.
+    from .types import Component
+    name_sym = expr[1]
+    name = name_sym.name if hasattr(name_sym, 'name') else str(name_sym)
+    env[name] = Component(name=name.lstrip("~"), params=[], has_children=False,
+                          body=expr[-1], closure={})
+    return NIL
 
 
 async def _asf_defstyle(expr, env, ctx):
-    from .ref.sx_ref import sf_defstyle
-    return sf_defstyle(expr[1:], env)
+    # Style definitions handled by OCaml kernel.
+    return NIL
 
 
 async def _asf_defmacro(expr, env, ctx):
-    from .ref.sx_ref import sf_defmacro
-    return sf_defmacro(expr[1:], env)
+    # Macro definitions handled by OCaml kernel.
+    from .types import Macro
+    name_sym = expr[1]
+    name = name_sym.name if hasattr(name_sym, 'name') else str(name_sym)
+    params_form = expr[2] if len(expr) > 3 else []
+    param_names = [p.name for p in params_form if isinstance(p, Symbol) and not p.name.startswith("&")]
+    rest_param = None
+    for i, p in enumerate(params_form):
+        if isinstance(p, Symbol) and p.name == "&rest" and i + 1 < len(params_form):
+            rest_param = params_form[i + 1].name if isinstance(params_form[i + 1], Symbol) else None
+    env[name] = Macro(name=name, params=param_names, rest_param=rest_param, body=expr[-1])
+    return NIL
 
 
 async def _asf_defhandler(expr, env, ctx):
-    from .ref.sx_ref import sf_defhandler
-    return sf_defhandler(expr[1:], env)
+    # Handler definitions handled by OCaml kernel.
+    return NIL
 
 
 async def _asf_begin(expr, env, ctx):
@@ -601,9 +617,12 @@ async def _asf_reset(expr, env, ctx):
             from .types import NIL
             _ASYNC_RESET_RESUME.append(value if value is not None else NIL)
             try:
-                # Sync re-evaluation; the async caller will trampoline
-                from .ref.sx_ref import eval_expr as sync_eval, trampoline as _trampoline
-                return _trampoline(sync_eval(body, env))
+                # Continuations are handled by OCaml kernel.
+                # Python-side cont_fn should not be called in normal operation.
+                raise RuntimeError(
+                    "Python-side continuation invocation not supported — "
+                    "use OCaml bridge for shift/reset"
+                )
             finally:
                 _ASYNC_RESET_RESUME.pop()
         k = Continuation(cont_fn)